WTB - driver's side rocker box(?) parts

[1972K5]

Hey everybody, 1st timer here, looks like a cool & informative group!!

Anyway, I was wondering about a source for the driver's side "rocker box" as I've seen it called in the forum, or what could be described as a cab floor support... Basically the long, box-like structure that runs length-wise with the rocker, tapering up on each end, pretty much stretching to the front & rear wheel-wells... Looks to be made of several parts bolted together, but the main channel appears to be one piece...

Looking at the sheet metal available for the trucks, it seems they are quite a bit different in this area for the Blazers/Jimmys, is this correct?

Thanks!!!