Here is Spintech’s site. Mine were 3” thick but now I noted they make a 2-1/4” thick case with up to 2-1/2 inch outlets. They are aggressive in sound but cruise well. They also have oval inlet/outlet mufflers. If I were doing mine over with the fairly mild stoked 428 again with 480 hp, I probably would have run 2-1/2 to the mufflers and 2-1/4 tailpipes to make for slightly more clearance around the tires.
https://spintechmufflers.com/mufflers/