I did lot of sounddeadner in my FJ40, then the carpet kit from cruisersolutions. I liked his carpet kit, because it was very complete - covered the tank and side pannels. It made a big differeance..
https://forum.ih8mud.com/40-55-series-tech/259276-diy-headliner-install-carpet.html
I love that setup! Is that Quiet Crap? I'm going to do that on my 76'
As far as rust and stuff, I'm going to sodablast the body, put some rust inhibitor or POR 15, prime/paint, Quiet Crap and carpet it.