Ye ole nightmare vibration at 55 mph

Have a 87 sport. Had severe vibration when you hit 45 so I had the tires all rotated and all weights taken off and a fresh balance as well as a new trans mount not from china, both u joints and had to use 4wd ones as the ones autozone had on website for 2wd wouldn't fit but the 4wd ones were identical to the old ones. Also replaced the idler arm bushing. When the truck was up on jack stands everything seemed very solid and had no visible play. I did notice my torsion bar bushings are cracked up pretty bad while doing the work earlier. After all that it did seem to help as it is now 55 when it gets bad. On the trans mount I didn't know what the pin in the middle of the mount that secures on top with a nyloc but. Its a 3/8 18 I think but there isn't really a way to hold it. My old mount had it tack welded on top as it's flat on bottom. Should that nut be tight. Maybe y'all have seen the mount and know what I'm talking about. Guy said all my wheels balanced out good but they self center on balance machine but truck has to rely on lugs to center I believe. With new trans mount it still clunks in gear sometimes too but not every time. Fluid that came out of trans was unlike any I've seen. It had no red tint to it. Im sure it may need shocks, but steering has no play just wheel not centered driving me crazy. Doesn't really pull none. All ball joints seem to be ok as there isn't any movement and they are tight. I think that maybe just because the rubber parts may look ok they are all old as the truck probably hasn't ever had any put on. So I guess next will be both motor mounts, control arm bushings, torsion bar bushings, and so on until I get it to stop. Any suggestions, tips, anything to look for. Thank you.