Custom TOMY/Plarail EMD GP-7/9

Sorry, but Salty is too short for this, and has coupling rods. Also, the shorter part is actually his back, not the front. If you were to use him, the motor would have to run backwards and the coupling would have to be moved to what would normally be Salty's front. A much better option would be to use a (modified) Dunbar from the Chuggington line since the character is (loosely) based on a GP-38 and therefore is closer....

Well, it clearly isn't going to be a dimensionally accurate scale model, so worrying too much about relative size is beside the point. Remember that these are toys and small switchers are depicted as being the same size as large road engines. Dunbar might make a fine later era Geep with a low short hood but appears to need more modeling work to get there. Salty's basic configuration appears to work for an early "high nose" Geep set up to run long hood forward (as was the practice on a number of US railroads).

Keep in mind too that UCWepn himself used a Salty to model a Victorian Railways T class, which is based on the EMD G8 and broadly similar to the GP series in real life. I think that worked out pretty well, don't you? So why dismiss another, similar conversion out of hand?