66 crossmember and other questions

[66BigBackWindow]

So from what I can tell, the rear cross member, just ahead of the trailing arms, is the same from 63-72. The deeper I get into this truck I find more and more that maybe multiple PO's have butchered. The truck was an original power glide but now has a TH400 that is literally just resting on the tranny cross member and the engine is not attached to the motor mounts. It has been converted to a one piece drive shaft, unknown vintage with a dink in it at the cross member location. The rear cross member has been torched on the lower side, I assume to remove the carrier bearing from the original two piece shaft. The truck was lowered by heating the coils so maybe the cut out was to provide lower clearance for the new shaft. I have a yard close that I could easily gain access to a cross member, or should I just buy a new one. I plan on replacing the old coils with new lowering springs, 2" up front and maybe 4" in the rear. Will I run into any clearance issues with this set up? Who has some experience with this?