Jeff,
I'm just getting into this stuff so I don't have all those books, yet. Would be great if you could post a couple pictures.
I came across this one on the Denver library site, although there is conflicting information on it's renumbering. One site says it became 345 but that is not possible as evidenced by the domes. After comparing with other photos, I think it became 341. It appears to me that only 340, 341 & 342 got both domes replaced with the new style. It also appears to be the only other one with a single air pump (later in life anyway) aside from RGS 40.
I sure wish Bachmann had offered a straight side tender version.
Jeff