So I stumbled across something rather odd. British O gauge.
British O Gauge isn't 'odd' if you live in Britain!! Here, in fact, American 2-rail Scale O is seen as something of a novelty, but American HO & N are much more common.
2-rail O is the norm here; 3-rail is the minority interest, & I seriously doubt anyone in the UK would want to take what would be seen as a decidedly backwards or retrograde step of converting a 2-rail loco to 3-rail.
Main difference that affects things is the British use of buffers & 3-link (hook & chain) couplers instead of buckeyes; R-T-R scale 2-rail models come with these fittings rather than some form of auto-coupler as in OO & N (if you really want to find out about an "odd" scale, google the history of OO!!). No provision is made to fit anything like Kadees either, so compatibility with US O is Nil.
Also buffer & link couplers affect the minimum radius the models can take; short diesel 'shunters' & steam tank engines will take 48" radius at a push, as will old-time (pre-1980's) short 4-wheel wagons. Bigger diesels, longer steam locos & rolling stock take 6ft radius minimum, or else suffer a problem known as 'buffer locking', when stock takes curves that are too tight & the buffer faces slide past each other on adjacent vehicles, then snag when the train straightens up again. As UK homes are rather smaller than US houses, & generally lack basements, this severely hinders home layouts in O, which tend to be straight shelf 'terminus to fiddleyard' (staging) types. Bigger Clubs might build large 'oval' layouts in O, often designed to be transportable for Exhibitions. On the other hand, the fact that many British locos and stock were quite short does mean that small but interesting layouts are possible, more so than if using American stock.
Our 'transition' Era was the 1960s really, & is the most popular Era in general, as your slightly earlier 'transition' Era is on your side of The Pond.
As for any to show off...
This is my Minerva Models "GWR 8750 Pannier Tank", number 3675, detailed for the prototype's last few months of service with British Railways in late 1965.