Back in 2000, a couple of the old mod motor guys found the mac's to produce 2-3rwhp more than the bbk's on one of the original mod motor sites, which is no longer around. However, over the years, it seems the bbk's hold up a bit better than the mac's. Either one should work though. There are a bunch of options out there.
I have BBK L/T's on the Cobra. BBK is a great quality header. A lot of GT500's now are getting Kooks headers, so they must be the more popular choice now.
I've had a set of MAC's on order to replace my old pair. They had been in the car almost 5 years. They still routed the exhaust the same way they did when they were new. I cut them out to pull the old motor.
Well the MAC's have been on backorder for more then 2 months now. So I am going to pick up a set of BBK's this time around.