Swapping rear end question

You might consider replacing the leaf springs while you're at it. I just did the 7.25 to 8.25 upgrade on my '74 Swinger and I replaced the springs at the same time. I've already noticed the car looks better and corners better even though I haven't rebuilt the front end yet. Also, if you can get the driveshaft from the same car the 8.25 came out of, there's a chance it could fit your car without cutting. That worked for me (it was about 1.5" shorter than the one that was in my car).