All small blocks share same crank ?

I changed U joints. Vibrated before and after. Wheels and tires are brand new and balanced. Not the slightest slop in drive shaft front or rear. So that leaves out u joints, bushing and yoke. Tail shaft bushings usually leak when worn. No slop or leaks. Driveline doesn’t make a peep until I hit 70. Then it hums a little. I noticed no drive shaft weights when I changed u joints. So im thinking it needs balanced. Or driveshaft, possibly yoke is bent. I bought the car a year ago. It rides, drives, corners like a new car. Improved a lot of things since then. Just haven’t corrected the 70 hum. Pretty sure it’s driveshaft. I’m going to take driveshaft to a shop now that it’s winter. If that not shim rear end another 2 degrees. If no results. I don’t know.