Hello all. I posted this problem and some follow-ups a couple of months back on another forum. I received all the standard answers/suggestions, but I ran that forum out of constructive answers. I think I need some inline 6 experts to think outside the box. I puchased a 65 Mustang last November for my wife. Car has 200 ci inline, and C4 automatic. The car has been a mechanical nightmare. I have addressed and fixed all concerns/problems except for one. The engine has a terrible vibration at idle in gear. It is noticable in park, but not anywhere near as extreme as in gear under load. Just to fill in the background. Timing was set to 12 degrees with timing light and vacuum disconnected. Idle was set to 500 rpm in gear. Both engine mounts have been replaced and are on correct sides. Transmission was removed and overhauled (due to knocking noise at front pump/torque converter area). Transmission was reinstalled with rebuilt/new torque converter, new flexplate and new mount. Distributor has been replaced with rebuilt one that I added a Pertronix Ignitor to. Ignition coil, distributor cap, rotor, plugs and plug wires have all been replaced. Autolite 1100 has been overhauled and reinstalled. I have had no issue setting carb. or timing. Timing cover was cracked, so I replaced with a good used one. I installed new timing chain with gears, new damper/balancer, new water pump and thermostat when I reassembled. I have no vacuum leaks. I have checked, double checked and triple checked. Fuel pump is new with new filter in canister. I don't know the history of this car or the engine. The engine has been apart, but I still have not figured out why. Somebody (who shouldn't have been working on cars) had the timing cover off (which they cracked), and the head/intake off. They painted them the wrong color along with the valve cover and air cleaner, before they reinstalled them. I know they also had the transmission out before I did, because alot of things were loose and poorly reinstalled. I don't believe the engine has been out of the car, because the oil pan does not appear to have been removed or re-painted. I know this is alot of info, but I'm at my wits end. Could something be internally bent or broken or wrong? I know it is a stretch, but could the crank be bent, the cam worn out, or something internal? I would like some suggestions before I remove the engine. Once I do that, I'm in for an overhaul. I'm in too deep now to guess anymore. The vibration is definitely in/from the engine. I can hold the chassis, transmission, exhaust, body and the rest of the drivetrain and not feel the vibration. Nothing is rubbing anything externally. Thanks for any/all help.