Mike,
I think I can help you out some with your questions. I have already done the asking of the important questions to the game warden and this is what he told me. You are allowed to use rifled barrelled shotguns during the shotgun seasons as long as they are not under 20 gauge in size or more than 10 gauge. You can use either iron sights or a scope, or both, it doesn't matter to them. All you have to know is that a shotgun shell will chamber in the gun you are using. You don't have to fire it for him, you might scare the poor man to death.
I have been doing some conversion of shotguns to rifled barrel double guns. Call them what you will, bore guns or rifled shotguns, it doesn't matter one bit, to you, me, or the state of Iowa.
Any deer taken with any of the mentioned combinations is elligable for measurement in any large deer contest or inclusion in the Boone and Crocket book, etc.
If you are thinking of making up a conversion, look for a 12 gauge with a Greener crossbolt. I did one of these on a 16 gauge and it really didn't work out very well, not enough steel in the breech area to do a good conversion. It is also nice to have a push button type forend release or one of the lever type releases. That will help the forend stay on during recoil. Stay with a two trigger model, they are simpler, stronger, and cheaper, but most of all they are more dependable. Side clips are nice but not vitally necessary to the project. Good Luck.