Figuring Out Frankenstein

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I've been slowly working on getting my 72 K20 4x4 back on the road. Both axles were replaced at some point with 1/2 ton axles, but I have no idea what they came from, or if they even came from the same donor.

At this point I'm tired of trying to backtrack and figure things out. I haven't had any luck finding model correct axles near me, and this was never meant to be a show queen so I'm not worried about it being "perfect." Are there other 3/4 ton axles, and leaf springs, I can easily swap in so I know what I'm working with? This is my first project, and I'm trying to do as much myself as possible, so the simpler the better.