going to have to make them both, then have a custom cam. 272 is the biggest regrind I can find. with the header and 272 I had in mine it pulled pretty hard past 7k rpm.
no delta cams stocks regrinds for the mazdas. 272 and something smaller I forgot what it was.
I used the 272, home made header, and a weber on the stock intake. I agree with you on the size of the pacesetter headers that is why I made one.