These two Scale-Craft K4 chassis were tested just this morning after looking over several locos. Early version with center axle drive and a later one with the rear axle drive. Turns out the later one is rough due to lack of stack up on the motor install.
https://www.youtube.com/watch?v=42iGFNvshK8
https://www.youtube.com/watch?v=dzkFM-Pjv2Q
Also one of my Scale craft Mikado from a few years back.
https://www.youtube.com/watch?v=xX00w9e81FI
Neither of the K4's was insulated for two rail and I think they will stay that way.