Can the tail of the long shaft TH350 be swapped onto the TH350 short shaft transmission and vice versa, I would like to use my short shaft transmission without modifying the driveshaft. If not its no big deal but if it would work that would be great any advice is greatly appreciated.

 

You would also need to replace the output shaft. When assembling a transmission, the output shaft goes in first since it's at the back of the transmission. You can't just swap the tailshaft housings.