Found a locomotive that matches the On30 2-8-0 in 55n3:
Most of the On30 Bachmann locomotives will work in 55n3 if you are modeling post 1900 narrow gauge. The ten-wheeler is too large. The Mogul with a few Bowser parts will make a great 55n3 2-8-0. All that needs is the domes lowered.
Harold, I really enjoy your research and inventiveness. This scale seems to suit you very well and if I didn't have so much time and money invested (and limited years to go) I might switch. I liked your On30 and all your tips so I'm going to continue down that path. But will follow along as you go your way.
Dave Mason D&G RR (Dunstead & Granford) in On30 “Those who would give up essential liberty to purchase a little temporary safety, deserve neither liberty nor safety.”~Benjamin Franklin The 2nd Amendment, America’s 1st Homeland Security
I have found something to convert all my On30 equipment to 55n3. I believe the BLI C-16 can be converted to a ten-wheeler, mogul or a 2-6-2 in 55n3. Not having the magazine index sure sucks in finding plans.