Well, if that was all you had to do, that would surely be the way to go however, there are a "few" other things you would have to think about...
(the following is an itemized list of all the things you will have to change, broken down into 5 catagories: Front suspension, rear suspension, drive train, transmission, etc.)
FRONT SUSPENSION:
1. Drag (center) link. If changing to V8 with p/s from I6 with p/s, the drag link may be the same but I'm not sure. The power ram and pump are the same. For non-p/s, the I6/V8 drag links are different.
2. Inner tie rods (LH and RH are the same for manual steering but LH different for p/s).
3. Tie rod adjusters LH, RH (LH and RH are the same for manual steering but LH different for p/s) Note: For 6 cylinders with p/s, if you plan to retain p/s with your V8, these adjusters are the same, just don't interchange LH with RH.
4. Outer tie rods LH, RH (LH and RH are the same for manual steering but LH different for p/s).
5. Idler arm
6. Pitman Arm - Note: Steering boxes are the same whether I6 or V8 however, p/s equipped cars from the factory had higher ratio (lower numerically) steering boxes. The P/S boxes are typically designated with HCC-AW while manual boxes are HCC-AT. If you have HCC-AX it would be an oddity, since the handling suspension steering box was only available on V8 Mustangs.
7. Spindle LH, RH
8. Two front Hub and brake assemblies including hoses (Stainless Steel Brake Corp offers original Kelsey-Hayes 4-piston front disc brake set up using the same spindles the V8 drum brakes use).
9. Pair of front coil springs
REAR SUSPENSION:
10. Pair of leaf springs.
11. Rear differential assembly ('65-'66 'Stang 8" diff. is only one I know will exactly fit but a '57-'59 9" will fit, '77-'80 Lincoln Versailles/Merc Monarch/Ford Granada (LMF) bolts in but a bit wide axle to axle face).
12. Rear brake lines and hose that are attached to the rear differential assembly.
13. Emergency brake cable. Note '65s and '66s are different. The '66s use a single cable to both rear brakes while the '65s have two separate cables. Choose wisely.
14. Pair of 10"x 1-3/4" (coupe or fastback for sure not sure with Convertibles) rear drum brake assembly (your on your own if you have a 9", LMF have rear disc but parts are obsolete).
DRIVE TRAIN:
15. Engine (duh!) Don’t forget the ground wire that goes from the passenger side cylinder head to the firewall.
16. Radiator. If your V8 has a driver side output water pump you can bolt on a passenger side exit pump (late '65 - '66). Note: '64.5 and early '65s used a slightly different style that won't work on late '65 on up timing covers. Then you will have to hassle with getting all the accessory pulleys to line up. An alternative is get a radiator shop to mod your radiator to accept the driver side outlet water pump. Don't forget, if you have an automatic transmission, make sure the radiator has the ports for the trans fluid lines. I think the '65s trans line thread directly into the radiator cooling tube while the '66s used the rubber hose connection between radiator ports and trans fluid cooling lines.
17. Upper and lower radiator hose.
18. '66 motor mounts LH, RH (if your 'Stang's a '65, use the '66 motor mounts, '65 stuff is harder to get and the motor mounts have an extra bracket which is a bear to find).
19. '66 motor mount to frame bracket LH, RH (these are being reproduced and any friendly neighborhood Mustang parts place will have 'em. National Parts Depot has 'em fer sure).
20. You can reuse the alternator but you will need to get the correct alternator brackets to mount it (depending on other engine accessories). Most folks seem to get the engine fully dressed so already have the alternator, water pump, pulleys, and fan parts. Depending on whether you're installing a/c or p/s you will have to find appropriate pulleys that line up. Note that 289s and 302's made '69 and before had a three bolt crank pulley while 302s after '69 had 4 bolts.
21. '65 or '66 Fan and fan spacer if your engine didn't come with them. Beware, later fans and fan spacers or clutch fans vary in length and diameter.
22. Starter - match to transmission type
23. Exhaust manifolds (or headers), exhaust pipe, muffler(s) and tail pipe(s)+ hangers.
TRANSMISSION
24. If autotrans, you can use the 6 cylinder's C4 (unless your V8 is modified for more power) but you must change the block plate and bell housing for one that will bolt to a V8. Note: Very early '65 260-289s used 5 bolt bell housings and the '65 and later engines were 6 bolt. You will also need the V8 flexplate and torque converter. Warning: After '81 all 302s used 50 oz imbalance on their flexplate/flywheel and the harmonic balancer is different from the pre ’81 harmonic balancer. Also, '70 and later C4s had larger input shafts so match the torque converter to the trans. Don't forget the trans cooling lines, kick down linkage if '65 or kick down cable if '66. One last thing, if you're changing to an C4, make sure it's one from a car that had a floor shift selector and not one on the column. The shift lever on the trans (and I think the internal rod) are different. Don’t forget the Auto trans torque converter access plate.
If manual get a V8 3 speed or better yet a 4 spd toploader. You will need the engine block plate, clutch bell housing, flywheel, clutch disk, pressure plate, throw out bearing, pilot bearing, dust boot, clutch fork to fulcrum retainer, and clutch fork. Mechanical clutch linkage includes clutch pedal to equalizer bar (Z-bar) push rod, Z-bar, clutch pivot - engine side, clutch pivot - frame side, 2 felt washers, two clutch pivot balls, clutch return spring, clutch rod from Z-bar to clutch fork. Or you could chose clutch cable conversion. See Vintage-Mustang.com (
www.Vintage-Mustang.com) and search their forum regarding clutch cable conversion. See above auto trans info regarding 5 bolt vs 6 bolt engine blocks and correct flywheel imbalance.
25. Regardless of trans choice, you will need the appropriate trans yoke, U joints and drive shaft.
26. Set of tires (if converting a '65) and a set of five lug rims (don't forget the spare - Doh!). Grab 4 extra lug nuts, too.
ANNOYING STUFF:
27. Engine wiring harness. This harness includes the oil and temp sending unit wiring plus the wires that go to the coil.
28. Alternator wiring harness
29. Starter cable from solenoid. The 6 cyl’s negative battery cable may be a bit long but may be useable on a V8 – critical part is the terminal lug that is bolted to the block. 6 cylinder’s may have a smaller bolt hole.
30. Accelerator pedal linkage assembly. Suggest using the ’66 style with the extra arm on it for the kick down cable if you have an auto trans. The '65 accelerator pedal assembly was the same irregardless of manual or automatic transmission. The '66 manual transmission cars had the same accelerator pedal assy as the '65's. Only the auto equipped '66's had the extra arm on the Accelerator pedal assy for the kick down cable. The V8 throttle rod (The link between carb throttle shaft and the accelerator pedal assy) is different than the I6 bell crank linkages.
31. That little arm on the autotrans that accepts the kickdown cable ('66 and up) or the kickdown linkage ('65 only)
32. Fuel line. Yup the entire hard line. You're going to get vapor lock if you use the 6 cylinder's.
33. If you have p/s, Hose, p/s pump to control valve and Hose, p/s pressure, control valve to pump . Match to type of p/s pump you have.
34. 14" wheel covers (if you have a '65 and using stock V8 rims)
35. Two (2) "289" badges for your fenders. Hey, if you went through all that trouble to drop in a V8 you might as well advertise it. If you dropped in a 302 or 351 you'll have to make your own badges.
Any questions!
