7 1/4 to 8 3/4 rear end swap

You will still have to shorten your driveline if you swap to either the 8 1/4 or 8 3/4 or get the driveline out of the car you are getting the rearend out of.

To use the 8 1/4 you have to shorten your driveline 1.5"
To use the 8 3/4 you have to shorten your driveline 2.25"