Need Advice, Suggestions

yepp, you mentioned he had a convertor built I knida assumed the used the original case....I went thru all this decades ago and finally got a convertor guy to do what I asked..the results were awesome!!!
So what you are saying is if I remove the driveshaft completely out of the car and start it up and run it through 1st, 2nd, and drive and it does not shake or vibrate then it would be a driveshaft problem..correct??...sorry I am no mechanic as you guys have probably already figured out...