General Axle/tranny swap questions
Is it worth it? I think it is a few inches wider than my A body unit based on what I read about the C body rear ends.
IMO; Not a chance is it worth it.
In addition; you will need Big Bolt-pattern wheels, probably with a custom offset . But even if you get the wheels on, now you are limited to running them forever, cuz the body is altrady on the tire.. And not to forget, no matter what rearend you slide under there, your driveshaft will need to be shortened. And going from 9" brakes to 10", is likely gonna need to have the brake-proportioning re-engineered to prevent rear-wheel lock-up in panic situations. and finally, yur still sitting on those weiner LD springs, so you'll be needing something to keep the pinion angle in line.
I want to be able to use as a weekend driver so I don't want super tall gears.
For your application;
IMO
Just;
1) swap in a different 7.25 with a lil more gear, I mean every HotRodder in N.America who has more than 3/8 acre of property, must have at least one of those in the stack behind the shed, lol. I got two. and IIRC one of them is a 3.23posi. out of a 68 Barracuda. or
2) install a higher stall convertor, say a 2800; I love mine, or
3) Put a lil more bottom-end power, into the engine. I mean, the slanty has a stroke of 4.125, so...........
I plan to run a 360 stroker about 450-500 hp. Can the 8 1/4 handle this or should I only be focused on the 8 3/4?
Well then, on the street with street tires, yes you should be looking at the 8.75, but you won't be needing any help from the gears, so you can run any old gears that come with it......... at least for a while.... lol.
3.23s will get you 60 mph in first gear with either of the 904/727 Torqueflites @~6500. 2.94s will bring that down to ~5900. 2.76s to 5550.
But again, a stroker is really overkill for a streeter. A stout hi-pressure alloy-headed SBM is all the tires can maybe handle, and not even very well with a 360.