The problem with the short/long tailshafts isnt the length its the yoke attachment. On the short shaft its a bolt on yoke like on a rear end but long shafts have slipshafts for travel. As far as the convertor being weighted i dont think that will matter much. It was probably more for the engines benefit than the trans. I dont recall seeing any after market convertors listed as weighted or not so its probably nothing. Youll need to know if its a 12 or 14 roller sprag though. Not sure how to tell other than disassembly. Someone may know the signs of how to tell them apart visually
