Howdy,
It is a damned shame that the Marlin's reputation has been besmirched by the failure of some early models of their pump shotgun. I have a Model 30 in 16 gauge that, like yours, is the product of years of modifications to the basic action concept. The Model 42 was built after Marlin went into receivership and was re-started. Model 42's were the first of the pumps to have the "bullseye" in the stock, were assembled from parts on hand, and were given as premiums to purchasers of Marlin stock.
SASS has banned the Marlins as some have a reputation for shooting the breech-bolt at the shooter, but I have never seen or heard of this ACTUALLY happening. Have you 42 checked out and save it for hunting small game. Chances are that the choke is waaay too tight for anything but the meanest rabbits. My sixteen patterns like a rifle group at 25 yards.
Bitterroot