That year would be way too wide for an A-body. It's a good year to have narrowed though. Some of those C-body wagons had a axle shaft that can be shortened and resplined. If you're going to run a bit of horsepower through it, I think I'd just get a good set of aftermarket axles. To add/correct a few other items mentioned above....the 8 3/4 rear end started in '66 in an A-body and most of the '73-6 cars had a 7 1/4 rear... even 318 cars. If you want to shoehorn an F-body 8 1/4 in an A-body, you'll need new spring perches. The F-body ones are for the rubber isolated springs and have a different type centering pin.
On either rear end you'd have to pull an axle to see if it will respline. Most axle shafts neck-down inboard of the splines and are too small a diameter to respline. Axles that don't narrow are usually a good candidate for the respline job. A lot depends on how much narrowing you do to the axle housing. Once you get further inboard on the axle shaft, it starts to get bigger in diameter again. You'll have to take some measurements to see if where you propose to respline is wide enough to do it.
It depends on which vehicle you're talking about. My A-bodies all have an 8 3/4 except for one low mile virgin which has a 7 1/4. The '78 W250 has a Dana 60 and the '78 Motorhome has a Dana 70.
What do you want to know about it??
