I've got a Marlin 55 that I turned into a slug gun, it has one of these peeps on it. Give me a couple of days to research it, I think that it was made by Lyman. If you can get a gunsmith to drill and tap the receiver it'll take a Weaver side mount. The bolt raises too high to get a scope directly over the bore, but that'll allow you to use the peep sight if your scope fogs up.

How long is your barrel? The marlin came in two configurations; a 36" barrel which they called their goose gun (which is pretty ironic sincemine only has a 2 3/4" bore) and the model that I have had a 25 1/2" barrel with a poly choke. It was the worst choke ever, as you turned the adjustment it would throw the pattern in a circle around the line of sight, I guess that it had some concentricity issues.

Here's the best part, I cut the barrel down to 20", drilled and tapped the receiver, machined a custom side scope mount and glass bedded the receiver. Using Winchester 1 oz foster slugs I can hold a 3" group at 100 yards.