More info.
The access panel & insulation pad on the junkyard car I mentioned were in very good shape; the panel had a single 1/2"x1/4" rust bubble on the lower edge, otherwise perfect.
The ribbed floor panel was in good unrusty condition (which was a surprise). You are right, removing it from the junkyard car would be tricky (with no power/air tools available), but it could be done by hand (via my tried & true hammer & chisel/putty knife method). The only thing I'd need to know is where to strategically cut the metal in order to get what you want/can use & still not be too complicated for me to do. Double-layer metal is ok as long as I have good (hitting) access from above or below. Frame rails take a little longer. Removing a slightly larger-than-needed section that can be trimmed down later (ie: in a shop) is an option, as well. I'm free Sunday, & the junkyard car should still be there then. LMNO. :wink2: