[wild one]

You can use a rear from a 1964-69 chevy 1/2 ton truck, they are six lug axles and the same width from drum to drum as your factory rear. The driveshaft input should be the same making the spring perches the only item thant would need to be changed. As an added bonus they came with 3.07 - 3.73 gears, if you get lucky you might even find one with a posi unit.

I have personally helped two friends install this type of axle in task force type trucks over the years, and it can be accomplished over a weekend. Also, I've helped put one in a 1950 chevy 1/2 ton recently - that one required replacement of the closed driveline.