I'm nearly certain you have a Dana 44, same as in my 1960 GMC. Your last picture looks identical to mine:
[IMG]http://img534.imageshack.us/img534/3800/exhaust02.jpg[/IMG]These are very common axles, you should have no problem finding parts. They are very popular with Jeep guys and have been used in Fords and Chevys as well. You probably already know you will need the “other” carrier to go to a 4.10 ratio. The break is 3.90 I believe. 3.90 and lower (higher numerically) gears require one carrier, and 3.70’s and down require the other. Mine originally came with 3.90’s from the factory, which I swapped for 3.08’s years ago when I ran a turbo 350. About 7 years ago I switched back to a manual 4 speed and swapped the rear axle to 4.10’s requiring a change back to the other carrier.
Check with any local 4 wheel drive or axle shop and they should be able to fix you up. On my first swap I went with used gears/carrier out of a Chevy Blazer and they worked fine for many years, so this might be a consideration if money is tight.
The only oddity I found on my axle was the brake backing plates. They do not use a conventional emergency brake cable mounting hole. Instead they had a separate bracket that bolted to the cable and the backing plate. Replacement cables do not accommodate this mounting setup. After searching hundreds of vehicles for conventional backing plates, I gave up and had my son fabricate new brackets so I could install aftermarket cables with conventional retaining clips on my original backing plates. Perhaps these odd cable attachments were eliminated by 1963.
