My new '78 Shortbed has brand new 2.5" straight pipes on it that the PO slapped on there...really nice system, all up in the frame rails and stuff, welded. etc. I believe that it doesn't need cats. ANYWAY..I'm gonna get some Flowmaster super 40's for it, and it'll be loud. OR I can put some nice mellow mufflers on it and have electric exhaust cutouts behind the headers. Does anyone here run them? Will offroading and mud affect them?