I started by removing the rear seat, rear seatbelts, all rear plastic parts, soundproofing from the carpet, and tar soundproofing. I then used thin automotive carpet and spray adhesive to glue the carpet over the bare metal. The carpet is very light and the total weight of the carpet and glue is not even one pound. The improvement to the look of the interior over the bare metal is definately worth the extra weight. The car is also much quieter with the carpet compared to bare metal. These pictures show the interior without the front seats but I put the stock front seats back in for now. I left the mounting hooks for the seat back in place, I can lay the seat bottom in place and hook the seat back on those hooks in case I want to take more than one person somewhere.
The car rides much better with the extra weight out of it. It is suprising how little weight it takes in this car to make a difference in the way it accelerates and handles. I will get a significant amount of weight out of it when I replace the front seats and seatbelts with something lighter but that is something that will be done in the future.