I did a 305 to 350 swap, an auto to t5, and swappped in a 9 bolt, when I'm driving at 45 to 50 in 5th the car gets a really bad shake almost like its lugging but more exaggerated, I did a trans mount and a u-joint but it's still there what else could cause this? At speeds like 65 or 70 the shake goes away

 

Bent axle shaft? Warped disc? Worn bearings?

 

I think bearing would be the most likely, which ones do you mean @Base91