Thanks for the compliments!
We lucked out and didn't have to replace those two panels with the humps to clear the gas filler necks on dad's truck. In fact, I think those are the only two that we did end up repairing/re-using.
I don't think it would be possible to stamp those humps out exactly like factory without some very specialized tooling. However, they look as though they could be re-created by cutting an angled slice out of a piece of tubing (like exhaust pipe) and welding it into place over a corresponding U-shaped notch in the new panel.
By the way, if you need some new cross sills, we found out that the ones available for 67-72 fleetside wood beds will make suitable replacements. The plank width (and corresponding hole spacing) is different, but Mar-K (
www.mar-k.com) offers them without holes so you can drill your own to match the 73-80 pattern.