one-of-a-kind back seat

um.....what would you build it with? plastic sheeting and styrofoam? If you're good with construction stuff, then i'd reccomend you do that. It would probably be better. Make an outer wood frame, caulk the joints then spread some caulk all over the interior or the wood, use a thick styrofoam (you can buy 2" thick sheets at home depot), then get some thin plastic sheeting inside of that, get yourself some silicone. its in the caulking area. don't get a sliciconized latex, go with 100% pure silicone. that stuff will never freeze, crack, or anything. You can have a little hole cut inside the bottom of the styrofoam piece nad plastic and al for your drainage pipe, and make sure to caulk around that also. what I would do, to keep the water out of your car, is build up a little piece along the bottom then put the door on top....i've put a picture along the bottom. make sure every joint is sealed very well.

ok i'd like to say on this edit....GEOCITIES IS A WHORE!!!!

SCREW IT, GO HERE.
HTTP://www.geocities.com/dogbert0051/
then click on cooler.jpg

Use wood for a box, black tar the inside and use pink house insulation (styrofoam), then fiberglass it all in.

Or drop in a regular old cooler, for about 1/4 the price, and 1/10 the effort.