Difference between core support in 57 GMC and 57 Chevy

[Old57]

I have been searching for something to show the dimensions of the difference between the way the core support mounts on a 57 GMC and a 57 Chevy. The GMC is totally different and mounts lower and to the center of a crossmember, and the Chevy mounts on both sides of the frame rails. I have a GMC core support that I want to modify to mount like the Chevy version. Does anyone have anything that shows the dimension differences, or have both frames that could take measurements and let me know?