75mph vibration

I will check the driveshaft spinning tonight once it's all back together again (almost there haha). The shop is reputable, and hell my dad works there and put the tires on the car in the first place.

As for freeway RPMs, I'll double check my speed with a GPS at some point, but according to my build sheet the car has a 2.71 rear end in it and even looking at them now the tires are in fact 225/75r14 as I thought I remembered. I have a small tach in the car mounted below the ash tray (ya know hat little $40 one at Advance Auto Parts) so it's kinda hard to read on the highway. But yes, it most definitely did not read past 2100 RPMs while doing 70. However, the speedo gear is the original one that's probably set up for the stock size smaller tires, so it may be off a bit. As I said, the car is a 100% original barn find car with 33,000 miles on it, and I'm the second owner. Besides the tires, everything else in this car is stock.