I live in sd and I'm pretty sure that you can't do anything before the cats. That's just what I have heard though. Sock cats you will definetly need and it can't be over 95 decibles
65 Mustang coupe
306 H/C/I, holley 4 barrel, T5, Hurst Shifter, Subframe connectors, 8.8 w/ 3.55 posi, 4 piston front disc brakes, SN95 rear disc brakes, shelby drop, 620 springs, Mideye 4.5 Leaf Springs, bilstein shocks.