On the vibrations...My 85 had/has it. I replaced motor mounts and the vibes moved to above 80mph..a range I could live with.....well yesterday the vibes came back at 70~75mph.

I am going to put the rear up on jacks and drive the car (rear wheels free wheeling)...if no vibes then I will rule out flex discs, driveshaft support, trans and diff mounts.
My front end pieces were given the okay by an indy but if the vibes persist, I think all new rubber in a 21 year old car isn't unreasonable.

I have also heard the rear subframe mounts can cause this but have no layman's method of checking them.

Pls. post all success stories for us in the suffering.

Don