The Athearn Roundhouse/MDC HO locomotives lend themselves to making smaller logging and mining locomotives.
55n3 allows the logging and mining aficionado options. The Tichy Trucks with 36" HO wheels become REAL narrow gauge trucks, 3-1/2' wheelbase trucks with 23" wheels. The Bachmann log cars fit right in as do the the Tichy Ore cars. All the Tichy Ore cars need is one trussrod removed and a 1/16" wide strip added to the frame to be 55n3.
(Click Images to Enlarge)
The Roundhouse 2-8-0 and a "Thomas" ore jimmy.
The Roundhouse 4-4-0 merged with an IHC/AHM/Pola/Rivarossi 4-4-0 shown with a drawing of the Sussex, Surrey and Southampton 4-4-0 #2.
The big drivered 2-6-0 is awkward in whatever scale it exisits. Smaller drivers can be added. That is a Bachmann On30 log car, looks good doesn't it.
The dreadful Model Power/AHM/Pola HO "Jack Workish" coal mine scales out well in Scale55
The 2-8-0 fits the small Baldwin Catalog loco.