Driveshaft length...not happy

So as we build this car, I get the driveshaft shortened for the build. The car was apart, so I scoured threads here for a C to C number!

65 Barracuds with 904 and 8.75. I had it made 49 1/2 C to C. We installed the drivetrain, then onto the driveshaft. Nope....its doesn't fit. WTF. Looks to me like 48.25 C to C would be correct. at 49 1/2, I could get it in...but would have to force it in. Car is on the lift, with max. rear drop now. NOT a good idea.

Lesson learned? don't go by numbers....measure it yourself.