Thanks for the input guys! I'm certain the driveshaft is wrong and probably waaaaay out of balance. I cut and welded it myself with no clue what I was doing. The only reason I did it at all was so I could have the truck mobile. I have no intention of doing any driving above 30mph until it has been replaced or fixed.

Also, the problems with the old transmission were due to many things. Partially to incorrect installation and also to some other stuff.

Quick update, I have the new transmission in, and everything is running great (now...). I had a few issues, but again, until I get some pictures and video up, there's not much reason to go into it.

This is still behind, but this can give you some idea of what I have been up to: