I put the engine on the tracks, power up, and throttle up. If it runs long hood forward, I figure it was meant to. However, many of the better models do have the F to indicate the front.
The Lionel PRR GP7 and Trainmaster are long hood forward, but the reading GP7 and GP7 as well as their Trainmaster are short hood forward. The giant clue, other then the F, is the engineer is also facing that way.
Finally a voice of reason. This discussion is somewhat moot. That is in that the toy train makers/suppliers baked this decision into the product.
And yes we can switch the wiring for the motors to get the engine to run in the other direction. But we would also switch the marker/class light wires and also the coupler wires which can be done.
Here are some of my diesels that for the most part were in fact made to conform to their prototype.
Lionel Hi-nose GP30's Southern and N&W:
Southern for the most part ran short hood forward.
N&W for most part long hood forward.
MTH Southern SD45's long hood forward and they LOOK great.
MTH second generation tooling Southern and Pennsy Train Masters.
But more important here are the pilot deck heights. Southern require a lower (step-down).