Cam & head upgrade 360 mag

Pjc, the M1 dual plane is a copy of the factory intake and as such, the ports should be the same..-ish.. I say the "ish" because there have been minor casting flaws as over the years, the sizes change ever so slightly. I would say basically it is a 1 X 2 port. If you measure it, it may come in with an additional 1/16. Is it a big deal? Not really. 15 minutes with a dremal and you can clean that up and match it to the head.

I do not know "exactly" how much power can be made by by the intake but by the time you start finding out the limits, you will have already swapped it a RPM or M1. Year back the factory to use that the stock intake was a capable intake. Thus the reason for them making an aluminum copy for there catolog and racers. There suggestion to move to there single plane, at the time, was justified and made sense. Even more so since at the time, there was no such thing as a RPM. Though the LD-340 & the Action plus were also a very capable intake.
The six pack was recommended at the 12 second bracket (arguable move) and the single plane M1 is (and this is weird) was recommended @ the 13 & 12.5 bracket and not again until the 10:90 bracket. I don't think your looking to run 10:90's or quicker yet. And you don't need that intake to run 13'S or 12.5's!