[Mike C]

I think the primary difference in the 10/20 frames was slightly thicker metal on the K20/C20 frames. There were differences in ball joints and other weight bearing parts.

I would have no qualms about swapping in a K10 frame with K20 drivetrain components and don't feel you would be giving up any capacity.

'72 frames are unique on the Blazer and Suburban in that the rear bumper mount is integral to the frame while it has never been on the truck nor was it that way on the 71 and earlier people movers.