Trevor,
Don't worry about getting flamed here - but, if you want to have some REAL fun, go over to the Goat and propose dieselizing the C&TS and STAND BACK! We know that's not what you're saying anyway. The Loop's ex-US Gypsum GE's are a custom variation of GE's then "standard" industrial 50 ton narrow gauge locomotive. The traction motors are special for narrow gauge - and like standard gauge traction motors take up all the space between the wheels and cannot be modified. The #15 at the Loop and the C&TS's #19 have even smaller traction motors that plug into a gear reduction case between the wheels. The USG units were equipped with CAT D-397 V12 engines and an oversize cooling system to handle the desert heat. With their modifications, the units wound up weighing in at 54 tons. The Loop uses them for train rescue and work trains - they are handy to have. There are some 3 ft. gauge end-cab GE 70 ton engines in Guatemala - I don't know if they are being used or not. They have Cooper-Bessemer engines in them that are hard to find parts for now.
Phil Johnson