7.25 to 8.25 Swap Questions

Nick96 said
My understanding is that so long as the 8 1/4 you install came from another A-Body and the your transmission tail length is the same as the donor car, you can use the driveshaft from the donor. If the transmissions are both 904's there won't be an issue, but if I'm not mistaken (which I could be), if the transmissions are 727's or manuals, or completely different from each other, you'll have a mish-mash of different trans-lengths and you'll have to shorten your driveshaft anyway.

Not quite. The Dodge Dart (111”) and Dodge Demon/Dart Sport (108”) had different length wheelbases. If you took a driveshaft out of a 318/904 Demon and installed it in a 318/904 Dart, and both had a 8 1/4 rear end, you would be short. If you did it the other way around, you would be long. A bodies had different wheelbases so it’s not as simple as taking a driveshaft out of any Abody with a 904 and 8 1/4 rear end and putting it in any other A body.

7.25" to 8.25" driveshaft?