I hope I don't add to your confusion, but I just went through this myself less than five months ago for my '87 K5. I returned floor panels from Golden State Pickup Parts because I could easily bend them with my hands and the fit was poor. Then I ordered the JC Whitney floor panels and was quite pleased. The JC Whitney panels were of a heavier gauge (difficult to bend) and significantly larger. I did not order LMC panels; however, I have used them for body to frame mounting hardware (expensive but good quality). For your information, the sizes and prices according to my catalogs are as follows:
JC Whitney 24 1/2 x 33 1/2 inches for $28
LMC 22 x 30 inches for $30
Golden State 22 x 28 inches for $50
Good luck.