Looking for drive line length info

I have been looking for drive line length info for my car and can't seem to find the accurate info that I need.

My car is a 74 Duster with a 340 and 904. It currently has a 7 1/4, but soon will be swapped to an 8 3/4 with 741 case or a 8 1/4. I was wondering if anyone knows the different driveshaft lengths. All I can find are with 727's

Thanks

My 71 demon with 904 and 8 3/4 rear has a 49 inch drive shaft....had it made a couple of years ago..