Good suggestions everyone! Thanks.

Yes, the tires are mounted on two sets of rims. One set is about a year old and the other are brand new. So I don’t think it is the rims or tires.

Both shafts I tried have new u joints.

However, I do have more than ¾ sticking out of the tail shaft. Maybe someone swapped drive shafts out before I got my hands on the car.

Does anyone have the correct dimensions for a stock factory driveshaft (71 GTX 440 auto 8 ¾)?

Thanks