gil-
I have a M12 Featherweight (12ga) that I bought fairly cheap because it had a Polychoke on it. The Featherweight was a pretty limited run by M12 standards and I thought finding an original barrel with IC choke would be impossible. To my surprise, it proved to be no problem (in fact I found a brand new barrel).
So perhaps rather than modify either M12, you might wish to hunt down a second barrel for each that best suits your needs and that way you can keep your shotguns as original as possible. In the event you find a second barrel and isn't exactly what you want you could modify it without consequence.
Doug
