O.K. This vibration was here before I did the motor and tranny work. I bought the car back in November and it did it then. However there were some other problems the car had and I concentrated on that stuff first. The car has always done this since I bought it. And I thought wheels and tires also but I sold the ones that came with the car when I bought it and got new ones. It still does it. This is what I have replaced and done and to no prevail still vibration. rear shocks and springs, front shocks and springs the shocks and springs are just OEM replacements. Tie rod ends , ball joints, steering rack, power steering pump, lower end of motor rebuilt, tranny rebuilt to incluse 3 of the actual gears, Aluminum driveshaft was balanced and U joints were said to be good. The car had a 5 lug swap done to it before I bought it. I know the front spindles are off a 94 not sure how they did the rear but I measured the rear one time and if I recall right from hub to hub it was something like 61 1/2 or 62 inches. The list of mods I had for this car claims the axle to be 28 spline 4.10 gear. Dont know if its normal when I was pulling the drive shaft out to pull the tranny the nflange on the driveshaft that bolts up to the rear when I removed it there was some fluid that dripped out from back there at the rear end. But thats that.
Parts changers end up spending lots of time and money and in the end you may be stuck with an empty wallet and still have a vibration. Spend the time to understand the vibration and isolate each component and test the component before you guess and swap potentially good parts. Your problem is easily solvable with a couple hours of time and a good diagnostic approach. Just my two cents. I worked as a technician at a dealership for many years and have learned that good diagnostic skills (isolating components and testing) and an understanding of the vehicle systems is the FASTEST and most EFFECTIVE method for isolating causes. 
