If your considering building an early Forney locomotive you might be interested in this page. The early forney’s would include B&B (Puck and Ariel), SR #1 SR #2, F&M #2/3, KC #1 and possibly others. The Portland locos SR&RL #5, #6, #7 are not included as they are available in Brass.
- Erie Limited Loco – A bit too small for any true Maine 2-footer, but might work for a WW&F #10
- LMB HOn3 Outside Frame 0-4-4T – Could be the starting point for F&M #2/3 S.W. Sargent or KC #1
- MDC 2-8-0 Inside and Outside Framed locos – The inner driver pair might work for the earliest forneys
- United HOn3 C&S 2-6-0 is nearly perfect for Hinkley Forneys with 30″ drivers and 48″ wheelbase (B&SR #1 & #2, Monson #1 & #2, and F&M #1)
Other Brass locos might work as well. Each would have to be inspected for it’s own merits.
Sn2 Trains 
I had one of those LMB HOn3 forneys. Mine was a 2-4-4 but probably the same model – albeit with leading truck added. It was my first brass model and I bought it because brass forneys are cool but with no other plans for it. I sold it a while ago and wish I’d held onto it. I really didn’t appreciate the potential it might have had for Sn2 and could easily see myself withdrawing it from storage occasionally to consider in this guise.
Chris