Covered the floor with Be-Quiet Ultimate sound deadener.
www.b-quiet.com/ultimate.html
Installed some of the sound deadner on the firewall back when it was 60° in the garage. Finished the floor last week when it was 95°, boy was that pliable and stick down easy in the heat! And to everything else if you weren't careful.
Then a wide strip of 1/8"aluminum faced bubble wrap type heat sheild. Bubble wrap heat shield also glued to the roof.
On top of that installed:
5692T61 Acoustical Polyurethane Foam Absorber, Adhesive Back, Skinned, 1/2" Thick, 54"w from McMaster Carr.
This will absorb sound waves bouncing around and insulate for heat.
Installed between truck and back seat also.
Have not driven the car with all this installed. Will give an update after I do.
Check out this site to help understand sound deadening.
http://www.sounddeadenershowdown.com/
Seams like I'm going a bit overboard on insulating but I want the A/C to to be nice and cool.
Several years ago I installed a small A/C unit reccomended for "coupes and small sedans". Did not keep up at all. Heat was coming in faster than the A/C could take it out. So installed a Vintage Air Gen II 4 vent evaporator. That helped out a lot but lack of insulation still left cooling less than desired. The foor only had the original rubber mat. Insulation and sealing of the car is AS IMPORTANT or more than the A/C unit. Plus install the largest unit that is feasible.