I ent through this. Here's what I learned. 1) Avoid the chrome MP type - they warp if you look at them too hard. 2) Iron (NAPA)or steel (440 source) works best. Some folks have had good results with billet aluminum (Mancini). Check flatness with a straight edge and trial fitting. If there's any rock when trial fitting without gasket you've got warpage. Use a belt sander or file to get the mating surfaces flat. Use some hardening type Permatex with a gasket as insurance. Don't overtorque - it will cause warpage and leaks.