When I needed a driveshaft made up for my 1940 Chevy, I went to a "reliable" drivesahft shop and asked if they make custom length driveshafts. They said yes and all they need to know was what type of input shaft that you were using on the tranny (32, 28 spline), what type of rear end you were using and the exact length from the tailshaft to the rear diff.
They came up with the proper shaft dimension, balancing and welded the appropriate tail shaft and end shaft U joint assembly.
Most shops do this routinely and only need a few dimensions. The key is go to a Hotrod shop that does this type of thing all the time. Experiance works!
RapRap
1940 ChoppedChevyCoupe
