You can use a 9.25 from anything B body later then your car also, all the way up to 78 Magnum/Cordoba/Monaco/Fury. Maybe some 79 cars.
The 8.25 and 9.25 are direct swaps, even driveshaft length. 8.75 will need a different driveshaft, but will also bolt in for the correct years, as above.
You can find a 3.23 in a 9.25 also. Or, if you find the housing, you can replace the carrier with whatever you want because they kept making the 9.25 for a long time so modern traction solutions will bolt in along with about any gear ratio you like.
I bought a 8.75 for my Monaco with correct ratio, and then found a 9.25 about a month later with the 323 sure grip, which is actually the correct axle for my police Monaco(78). I am too far away in WI for what you are after or I would offer you the 8.75 if you want it.
Good luck! Both of these axles are not super common, the 8.75 because they only made it for like two years early on and the 9.25 because decades of indifference about the mid 70's cars makes them scarce. People have stuff tucked away though, I am sure one will pop up.
