7.25 to 8.25 swap

The F-body 8.25 will fit, but it's not a direct bolt in. The spring perches are 44.5" center to center instead of 43" for the A-body. It's wider as well. A BBP a-body 7.25 is 51.5" wide flange to flange, the F-body 8.25 is 54.3". It's very doable but it's not the same. (It's narrower than the 68-70 B-body 8 3/4 in my duster)

Also, any 7.25 to 8.25 swap will require the driveshaft to be shortened a little.

So, at the very least you'll have to weld on new perches and have the driveshaft shortened. And if your current wheel combo can't be moved out an inch and a half without rubbing, you'll need new wheels too.

Here's some axle specs, there are some 7.25 and F-body 8.25 specs in here as well. An accurate 8 3/4" rear axle width list