They are 11 gauge stainless steel tube (ss) with 1/2" mild steel (ms) flanges. They are stepped up to 2 1/4" up pipes. They are the best flowing stuff we have.
These are intended for HIGHLY MODIFIED MOTORS ONLY!!!
Newer body style trucks require a coolant line relocation fitting.
These are for use on trucks WITHOUT conventional downpipes and have both headers and up pipes almost symetrical. There can not be a downpipe behind the cylinder head.
They are custom made to order so expect 1-2 weeks build time.