67 Barracuda Trans question

Thanks for the welcome. I'm glad I found this place, it's like an oasis of my kind of blood! After all of the advice about keeping with the 904...well I just had to try the 727. All went well until it came time for the drive shaft. First I had to locate the right size yoke and then I had to cut 5" out of the shaft. I thought it went well for my first drive shaft surgery until I got up to about 40 MPH. The car shook so badly I'm sure some bondo and rust fell out. I'm going to the dentist to have some fillings replaced right after another drive shaft surgery! Mopar-To Ya ,Richard