For noise .. on my 1993 ford conversation van and rv.. I used aluminized sound deadner.. hit favorite online store or a/p store.. there are many brands .. I tried the expensive stuff.. and it's great.. but at 1/2 the price the other is just has good.. I am on a budget and had a lot on area to cover.. so 1/2 price sound deadner for me.. 1 points order in bulk.. a lot of it.. do.. doors.. and floors and inside fenders.. on van.. which is same as yours.. maybe 4 big boxes.. save left overs for other parts of rv.. like gen bay.. you can't hear my gen run.. it can add up quickly.. so I did 1 box.. then 2 box.. as I could afford.. you have to wipe down with good solvent 1st.. follow directions on package.. in some places I used 2 coats/ sheets over each other..
Just my opinion.. take old pig of muffler off.. save it.. and add straight glass packs.. use slip type clamps.. in case you are not happy.. you can reverse.. but big difference..
If no smog in your area .. one if so inclined could gut the cat.. Hugh improvement.. but it's your call.. pull exhaust cat and muffler and experiment.. but if you go down this dark path.. I get a lot of flack.. then you must keep eng in top tune.. you will not pollute.. then there is a pulley that replaces the smog pump.. and I hate egr.. you can do that one too.. Hugh improvement.. just ideas .. not mine.. opinion.. but I is important to minimize polluting.. while getting long life and power..
More power rabbits..!!
Don't forget coolant.. and put the lowest temp thermostat you are comfortable with in.. I run 160.. no problem.. except if below 15.. I use cardboard and that worked great.. post a picture of your trans cooler.. I added big engine oil cooler on mine.. I get into outside temps 110 plus running front and rear a/c.. and never get past 180.. even while sitting in traffic.. keep extra serpentine belt or replace old one and keep as spare..
Good luck and keep us posted
2000 southwind storm, workhorse custom chassis with 7.4l vortec