[remist17]

Since I have not gotten much support I sat down at the junk yard and compaired several square bodies. My 87 had a 1 3/8 top flange of the frame and a 2 1/2 bottom flange of the the frame. The engine mounts center line to centerline was 17 1/2"

Looked at a 86 C10 Truck Top flange of frame was 1 1/4" bottom of flange was 2 1/4" and centerline to centerline was 16"
Looked at a 87 Suburban Top flange of frame was 1 3/8" bottom of flange was 2 1/2" and centerline to centerline was 17"

So to answer many people no these frames are not all the same.
Hopefully if anyone searches they will find this thread and shed some light.