Hi,
I, too have a '59 Chevy 3200 series pickup and have been through the wringer RE: rear axles. I went through the whole deal and brought it 'up to snuff' but I'm still wanting a posi unit. Yeah, I know posi's were offered back then, but just try and find one. A mid/late 70s Chevy rear axle will bolt up, just check the spring-pad spacing. NAPA has all manner of 'two-size' U-joints to mate an axle to a differential. I've seen these later rear-end units complete with posi, although they usually have pretty high-geared ratios (like around 3.08 or so). Later on, the spring-pad spacing got greater, thus requiring welding on new spring-pads, although that's not such a big deal.
Regards,
Apache Kid
