difference between c10, c20, c30 frames

[bgeraurd]

I heard the 4x4 k10s and k20s were the same but just had different axles. So I was thinkin what is the diffrence between the c10-c30 frames cause me and my uncle want to build a drw c30. We were gonna get a c-10 or c-20 longbed and put a 73-87 drw 3500 front crossmember and rear axle with some modified stepside fenders. Do the c-30s have the trailing arm rear suspension cause we wanted to bag it but not make it lay frame, and having the trailing arms would make it a lot easier.