1970-72 Chevy/GMC Frame differences

[Dieselwrencher]

I have a 72 C1500 long bed 2wd frame listed for sale. I listed it stating it has leaf springs because it was from a GMC but noted the frame is closer to a coil spring truck. I originally wanted to 4x4 swap the front of the frame but since the rear is shaped differently, I decided just to sell it. A member posted in the thread stating that this frame is basically a leaf spring frame, not a coil spring frame. I'm intrigued now and don't want to be misleading.

I realize the Chevrolets were standard with coil spring suspension and leaf springs were an option. And the GMC's were opposite. I also believe all the K frames had straight frame rails over the rear axle. They don't bump out in the middle of the wheel well/over the rear axle.

Here come the questions. I've had a few Sierra Grande C15s over the years but all were parted and scrapped. I never paid any attention to these frames. Same with C10s.

Were all half ton 2wd frames based off the coil spring suspension and have the bump outs over the rear axle? (C10 and C1500)

Is it correct that all the K, 4x4, frames were straight and had no bump outs?

In the pics below, you can see the center cross member has factory punched holes for the mounting brackets for the trailing arms. Yes, it is missing the cross member and reinforcing plates for the coils to mount to. I firmly believe these are a coil spring frame with leaf spring hangers bolted on the side.

Do any of you have pics of a leaf spring C10 that the rear rails are straight and don't bump out?

My experiences with these trucks are mainly C20s or K10s and K20s. I like learning new stuff on these trucks though. I've had a couple coil spring rear C20s but once again, those were pars trucks and were scrapped long ago.