Drive shaft length

I have a 67 Dart. I pulled the 7 1/4 rear out of it and am putting in 8 3/4 (has 904 trans). What should the lengts of the shaft be from flange (bushing/bearing) center to center. I would sure appreciate any help I can get. I have the service manual but it does not spell it out. Thanks.

[dschumers]

I don't know what the exact length is , but when I did this swap in my Duster last summer, I had the driveshaft shortened 2-1/4". Dennis

[BugEyedValiant]

I think it is about 51 inches. Dont have it cut to that length without checking for sure. I had a 48 inch shaft(center to center on the U joints) in my valiant with a 904 and 8 3/4 and your dart should have a 3 inch longer wheelbase. Hope this helps