1. Falcon Six hand book!
2. Keeping it simple, place a huge limit of budget, and have a compression check done by a mechanic. Fuel isn't cheap anymore, but too much is made of the cost. To improve the highway fuel consumption 40%, like going from 17 to 24 mpg, then you have to spend the same amount of money you'd save on fuel in a year. If you think you'd save 250 dollars, from a 40% improvement, then you'll have to spend twice to three times that much up front to get that saving. There is no other way
Then focus on
3. the ignition
4. the carb ,
5. The exhast. There is a special adaptor which will hlep mileage. The mufflers need to be low restriction but don't re-do the whole exhast system. Old mufflers really gum up the exhast, and best economy happens when back pressure is moderate.
The details follow.
With what you have, you could just add a good DU1 igniton form FSPP. 95% of problems with tuning are related to problems with the quality of parts in the ignition, so a great ignition, good spark plugs and good wires are the best start.
Since your car is automatic, it's much better to by up some old 1968 or 1969 1-bbl Autolite carbs with the alloy adaptors which fit your cylinder head. Pony carbs is fine if you don't mind the cost. Or get them from ebay with the stock C4 kickdown lever and get to know how it works. Learn how to tune the idle mixture from the oxygen sensor, then learn how to select the best one with the leanest main jet via the same oxygen sensor.
There is a bimetellic heat valve on some Mustangs for automatic choke operation. I'd suggest not using that.
When the cast iron exhast header is removed, you risk breaking off the iron cleats that mount the bolts to the head. In side the cylinder head, under the carb, there heat stove should be blocked off by using the Clifford port divider. When this is mounted via a heap of muffler cement or JB Weld or Devcon, it shields the carb from too much exhast heat. Just make sure you peg it in well. Exhast heat hurts fuel milage after the first 5 minutes. Then get a manual choke conversion.
Then have a muffler shop weld a 20 dollar oxygen sensor housing to the exhast pipe header tube. Grab four old one wire oygen sensors, and hook one of them to a cheap multimeter. All you need is a nice long line so you can read the voltage in the car while you cruise, or in the engine bay while you tinker with the carb. There is information on how to do this.
Later on, get a 1978 (D8) to 1984 (E1) head, you can then step up to a later Holley 1949 carb or Weber 32/36 or 5200 carb, and then tune that up.
I was wondering what could be done to this engine to maximize gas mileage out of it; I would like to eventually make it my daily driver. (I have not got it running yet-needs starter & exhaust)
