Pulsating vibration while cruising??

I started with pinion angle and learned I had a 2* difference and thought the shim would do the trick. The car feels stronger but my vibration was still with me. So I swapped out both universals and had the shaft balanced. It was worse after that but the shop didn’t have replacement bolts and had trouble tightening the old rounded ones. I got new bolts, and a really good 3/8 wrench and tightened it up. Got really close, so flipped the shaft 180* and tightened to spec (not sure how I’d translate to metric!?) and it feels pretty good. I’d say 90% there.
BTW I was certain mine was coming from the back....have you ruled out your torque converter?