WHAT KIND OF HEADERS WITH MAGNAFLOW

I can't decide if there are more active header threads or timing adjuster threads.

Hooker, SHM, Kooks, and BBK are all respected headers. MAC is a cheaper and less respected option. Your exhaust doesn't care one way or another which one you use, although you will need to chop up that X-pipe to make it work. BBK and Hooker seem to be good compromises in the price dept.