Being a Rio Grande Fan, I am very partial to F-Units. When I think of the Rio Grande F-Units in 4'8 & 1/2" between 1940's to the 1960's as being the work horses for the mainline of most Standard Gauge on the D&RGW, I think of 2-8-0's in 3' Narrow Gauge as the work horses from 1880's to the 1910's and the 2-8-2's from 1920's on to abandonment. Though there were other types of engines on both the Standard and Narrow Gauge Rails, these engines seem to always be found pounding the rails to get deliveries through. Colorado Railroad actually has the best of both worlds to me as they have the 5771 and 491, and 346. What an amazing feat it would be to have 5771 run again on their Rails.
I love the Dual Headlights these MZ Units have, sure would be sweet to see them on the RG&SLRR somewhere in the future if it permits, painted in Black and yeller paint.
Still a Student,
Dave