Then buy a system. DO NOT try and find a down pipe at a RIG shop. Just buy a 4in system. Use the down pipe cat and after cat piece, then sell the rest.Id like to run 3.5 or w/e stock is and just fun it to a 5" tip.
I agree with this too. If you need a larger down pipe, Then just buy the whole system. Or call guy's like this whom have shops. Some folk do not like to work on there own truck, So places like Extreme install their exhaust for them. So maybe they have stock 3.5 downs sitting around or bends for that matter.i've done a few of them using pieces of the tailpipe and finding the right bend. usually if you get an aftermarket 4" t-back there is enough in there to do what you want.