should you decide to do the porting, spend the extra money on a good carbide bit. single cut for aluminum and other soft and/or non ferrous material. double cut for ferrous stainless, and other hard materials(yes use this one). dip the bit in oil for cooling (cutting fluid or motor oil, i use motor oil because cost). i have a "tungsten/carbide" cutting bit, and it seems ok. so if you have a choice, i wouldn't pay more for the added tungsten. usually your local weld shop will carry good stuff. or if you must save a few pennys, try these:
this is what grainger has to offer and
this is what enco has to offer