What do you have? Do you have a slip yoke already? If so, slide the slip yoke into the transmission and bottom it out. Then, pull it out 1" and measure from the center of the u-joint hole on the slip yoke to the center of the u-joint cup on the rear end yoke. Done.
I have to take a slip yoke off a driveshaft that I know is not the correct one. (The driveshaft is about a foot and a half too long but it has a 904 slip yoke). I don't have a slip yoke loose on a shelf or anything.
