Driveshaft Length
I can answer this. I have a '75 Duster (108 wb ) with a 727 and an A body 8 3/4 rear end....I don't think the engine plays any part in the length.
I didn't want to cut my /6 drive shaft up to make it work
Credit for this answer goes to crackedback and 72Swinger340.
I had been looking for a long while.
Part number 2883690. It fits a 108 WB car with a 727 and 8.75.
A rough measure with a tape measure is 45 inches, the book says 44.99 inches so close enough
I installed mine last week. Fits perfectly.
Ian.