It's been awhile since I drove the car (it's undergoing a minor "freshening"). The vibration is speed sensitive, feels the same as a bad u-joint. Haven't been able to test drive it yes since the front clip is still off. Tailshaft bushing is new. Flywheel has been the same for 15 years. Engine is a 400 stroker with a 4 speed. The last few years the vibrations have gotten much worse so I don't think it would be the flywheel. Also swapped to a different set of tires with no change. Hoping it's the mount but it will be a few weeks, hopefully, before it's back on the road.