Guess I'll try again to bring this to a concise close. The adapters I had made were successful at reducing the vibration issue to the point I have no remaining complaints (smooth up to 75 mph which is as fast as I've gone so far). I fought this issue for years and worked through bell housing alignment, harmonic damper, motor + transmission mounts, drive shaft, u-joint angle and probably more stuff than I can recall now. I discovered and fixed a bad rear bushing in the Muncie (thanks to 5speeds.com) a bad balance job from an engine shop now out of business, a misaligned bell housing (fixed with .007 inch offset dowels) and now the hub adapters. I undertook them because my alignment shop suggested them after rotating my wheels and finding that the vibration changed slightly with each wheel position but never went away. Then JohnZ suggested the road balance method used by shops with such balancers which helped a bit more. Now that the journey is over I just thought you all deserved a summary. CRG has been a simply awesome resource for me and my restoration of two 69Z's.