Saginaw 3 Speed Help

I have been having issues with drive lines lately and I have come to the conclusion that i need to turn either the shaft in the transmission or a little bit of the teeth off of the yoke. I have access to a lathe and was trying to figure out if anyone knows what the O.D. of the tail shaft was. This will be the smooth part passed the splines in the transmission. I have a 29.5" Drive line with an 8" yoke and it bottoms our just before it gets to hit the chain. I don't have the resources or the time to just take the tranny apart right now so im going to have to turn the yoke. I would rather turn the inside of the yoke so i still have partial splines on the shaft instead of just trimming the yoke off. 

Thanks in advance!