450,
In answer to your question about an American shotgun with only a "third bite", L.C. Smith, Savage, and A.H. Fox, all made guns with only one spiral lock up and all Could be considered to have only the "third bite" as they all interact with the rib extension only. There may be others that I have missed, but all these have a circular rotating lock that is a type of screw lockup.
I don't consider any of these to be fit donor guns to build any kind of rifle on. I would do a 20 gauge rifled slug gun on one, but not a high powered rifle cartridge, of any sort. I personally know of at least two L.C. Smiths and one 1894 Remington that were converted to 45/70 and have held up, so far. But I won't do one on either of these and I don't think it is safe for anyone to convert one. Bob H.