Custom Exhaust Question

[WankelsRevenge]

So I'm planning on making a semi custom exhaust for my 86 NA 6port motor. What I have so far to work with is a verified Racing Beat REV-II exhaust for a Turbo-II as seen here
http://www.racingbeat.com/RX7-1986-1...ems/16425.html
but just the Y-pipe and muffler.
I plan on also using what I believe to be a Pacesetter header as seen here
http://pacesetterexhaust.com/84-92-m...7-headers.aspx

If possible I want to connect the two using a Racing Beat presilencer, if I have enough room to install one. My biggest question is the flange on the header, would it be a generic 2.5" flange, or something I'll most likely have to get custom made?