Removing the sound deadening tar from the floor can save a few pounds. I didn't save it all to weigh it, but I've seen estimates at 20-30 lbs. Since I'll be putting carpeting and a heavy roll bar in the car, I figure I can start to compensate by removing this tar.
This is the second time I have done this. The first time was on project rally beater, and I just used a hammer and large flathead screwdriver. Doing it in the dead of Ohio winter helped too, but it still took a few days of work and it wasn't fun at all!
This time around, I took the advice of some others and got a 10 lb. block of dry ice. THIS IS THE WAY TO DO IT!!! I got the whole thing done in 2 hrs. Just get a block of dry ice, and set it bare on whatever spot you are going to work. Let it sit for a few minutes, and you will hear the tar start to make some popping noises as it contracts away from the floor. Then just move the ice to the next spot, take a hammer, and beat the heck out of where the ice just was until a chunk flakes off. You can hammer it all out, or I found it could just be pulled up by hand once it was started.
Try not to touch the dry ice, and by touch I mean bump into or make any sort of contact... I got a few spots on my fingers that are hurting now where I just taped my hand against it for a fraction of a second :) Wearing some gloves would probably be the best idea.