Treborwolf,
The Convert-a-Mount is Ideal for an Ithaca, since the barrel and receiver use the interrupted threads to lock themselves together. The Remingtons usually don't fare quite as well, unless you pin the barrel to the receiver. That said, my son has a saddle mount on his 870 and it is very accurate and returns to zero, but not as fast and simple as the Convert-a-Mount. Not all 870 barrels and receivers lock up as tight as my sons does though.
My first slug gun was not even a slug gun at all, a brand new 1975 12ga Ithaca/SKB XL-900 autoloader that my dad bought me for my 14th birthday. I later tried a Tasco side mount on that, but didn't work very well due to a poorly designed mount. The barrel and receiver has the tightest tolerances of any repeating shotgun I have ever owned or handled. I also tried one of the receiver mounts on a brand new 1100 LT 20 Slugger (beautiful gun) back in '88, couldn't get that thing to hit a 55 gallon drum at 50 yards, all because Remington's machining tolerances were way to broad (very sloppy). in '89 I traded it for an Ithaca Model 87 Deerslayer Combo (rifled), but had the receiver tapped. It was very accurate, but was not made to the quality (jammed alot) that the old mans Model 37 was. Traded that in and bought a Mossberg Model 9200 Slugster Combo that has the cantilever mount rifled barrel. This was and still is a very accurate setup. Now I shoot a 20ga H&R/NEF Ultra Slug Hunter LE, it is the best Slug Gun I have ever owned or shot.
I also have a Browning Sweet Sixteen Buck/Bird Combo, but that will never wear a scope.
Whatever mount you decide to go with on your 870, the weakest link in your accuracy will likely be the barrel/receiver lock-up. Hope yours is tight and not sloppy. The Convert-a-Mount is the least intrusive of the receiver mounts, allowing you to switch from Buck to Bird in the quickest amount of time. I think you are on the right track, I went the expensive route. Just wanted you to know what didn't work as well also. IMO the best mounts are either the cantilever mounts or a weaver style rail mounted directly to the barrel like my USH.
Also watch out for the Weaver PLASTIC (Made in China) saddle mounts that Wally World (Weaver Brand) and Gander Mountain (Guide Series Brand) are selling. Those MAY be close enough for a turkey load, but would have to be a joke for a slug gun. Still can't believe it, and I seen them at both places with my own eyes.
Winkman,
Just in case you did not already know it "Ithaca Gun Company acquired the assets of Ithaca Guns USA, LLC in June of 2007". They are once again making the Model 37's in several different configurations. Featherlight, Ultralight, Deerslayer II, and Deerslayer III. They are located in Upper Sandusky, Ohio. Enjoy!
http://www.ithacagun.com/index.htmlhttp://www.ithacagun.com/firearms.html