When I built my '56 3100 in 2003, I got rubber flooring from the old Chevy Duty. Whoever you use, just make sure that if they offer two versions (floor shift/column shift) you get the one for your truck. However, a note of warning. I can see from your pictures that you are as picky--as I am--you won't be happy with bumps, buckles or ridges--anywhere. You'll want a nice smooth installation.
Make sure you install the rubber over insulation/padding on a warm day with the help of a heat gun. Add extra padding as needed. You may still have to modify it using a razor knife to make a cut along the half-moon where the humps meet at the gas pedal and possibly from that point cutting a small pie shape back toward your seat. If you have to do so, use a piece of rubber (pond liner, rubber roofing, inner tube) and black gasket maker or self-adhesive rubber roofing or gutter repair material to back your cuts. Your modifications should be almost invisible if done right.
You may also want to use a piece of rubber around your dimmer switch, clutch, brake, etc. holes as needed.
If you tend to get the hotfoot from your manifold location against the firewall right under your gas pedal, you might be interested in checking the availability a piece of floor (firewall) insulation material from Moore Power
www.moorepower.com (402) 786-2887 in Waverly, NE. Call and ask them about it as it's not shown on their website. (their main business is manifold coatings)
You don't need to cover the whole floor--just the area that tends to get hot--I think I got 3 or 4 square feet. It's the best investment I ever made--bar none. Almost zero heat transfer through the material--you can put a blow torch on one side and feel nothing on the other side. The stuff is used in stock cars (about 1/8 in. thick, cut with scissors). I went from burning the #@&% out of my right foot within 30 miles from home and using the cruise control just to keep my foot from being medium rare to "AHH!, let's go for a long ride, honey!"
Good luck.
