Mark;
Kozo Hiraoka designed and wrote up most of his model locomotives in metric. North American prototype, but interesting, as 4 of them are geared locomotives.
Nick Feast's Q1 as written up in ME is metric, but he does use some inch fittings.
I've also got plans for a 2-6-2 in 3-1/2" gauge from the Dutch Modelling Group. (DB23)
Now, these are locomotives, but the Dutch group **LINK** has all kinds of plans in metric.
Jason has shown past knowledge in Continental stationary engine plans/kits, so he's a good resource, IMHO.