Trouble finding U-joint info on 14 bolt swap

[Barnfind46]

First I want to thank every one for all the great info that is shared here. I am in the final stages of swapping out my rear end on my '68 C-20.I replaced it with a 2004 Chevy 2500 14 bolt rear with disc brakes and 3.73 gears.My question is did any of you need a conversion U-joint to go from the original driveshaft to the newer rear end and did you have to shorten the drive shaft 4"? The 2004 apparently takes a wider (bigger)U-joint. I would appreciate ant input on this. Thank you.