Looking for info on '72 swb rear axle setup???

['72MotherTrucker]

I have a '72 swb and I thought that the rear would be leafspings, but there is a coil sping setup. Is that stock? Is it functional or is swapping in some other pieces, parts a better option??? Any help and suggestions are much appreciated, I just got the truck for $225 b/c original owner couldn't keep up on the insurance, and the frame needs some welding near the rear axle. (OHIO RUST), but the thing runs/drives nicly for that issue. I also was wondering about how you find the rear gear ratio?? Door code, axle tag, where do I look???