The seat mod was the easiest part.
If you've ever seen a plastic seat pan, you'll know that they are not smooth and even, but rather have lots of high and low spots in the mold. I sprayed the top of the seat pan with expanding foam. I gave it a night to expand then came back with a hack saw blade and trimmed it across the top along the entire length. This gave me a nice, solid, flat seat pan. Then I cut out a piece of aluminum flashing the same size at the top of the seat pan and riveted it on. I next covered the seat with carpet padding, then 1/4" foam and finally a sheet of plastic before putting the stock seat cover back on.