I work for AMD as our QC guy and am also involved with R&D, marketing and several other facets of the business. It is definitely confusing, we apologize. We have yet to come up with a better way to label them.
Looking at your pictures, you're definitely going to need some floor patches, these are the more accurate OE style ones:
Front Cab Floor Pan Half - Replacement Style - RH - 73-87 Chevy GMC Squarebody Trucks C10 C20 C30 K10 K20 K30 Suburban Blazer Jimmy RH = Passenger Side Note: 21" W x 29" L ; Drop down is 15 1/2" L If you're in the midst of a restoration project for your Squarebody Chevy GMC truck, then you'll...
www.autometaldirect.com
For the inner rockers, the "full" inner rocker is what you're going to want. It's more like the original and has the little drainage/wiring channel in it:
Inner Rocker Panel - Full - RH - Inner Rocker Panel Chevy GMC Squarebody C10-K30 1973-1987 RH = Passenger Side The inner rocker panel is a vital part of the truck's body structure, providing structural rigidity and support to the vehicle's frame. Over time, exposure to the elements and road...
www.autometaldirect.com
The "backing plate", some trucks had and some didn't. We have yet to find a rhyme or reason for it, but we wanted to offer it. If you look up under your truck, you should be able to see the outer rockers, the inners and if you have a third ply there, you have the backing plates as well.
You definitely also want to replace those kick panels, they were welded to the floor originally, not just seam sealed and those have rotted quite a bit further up than they used to be.