[Big Kev-O]

I converted my 68 GMC from leafs to coils. The C20 frame has the same curves section/ bump outs (circled in the picture) as the C10. The frames is about 3/32" taller between the top and bottom of the frame rails and is made from slightly thicker steel. Leaf spring frames do not have rivet holes in them for the coil style shock mount cross member / spring perch. Leaf truck don't have panhard bars which is another requirement on coil trucks.

The hardest part of converting a leaf truck to coil springs is locating and drilling the holes for the coil style cross member.