the proportions are WAY off. it's way too short to even count as a standard gauge engine

Fun fact, it's not standard gauge. It's 750mm!
Google searching "Minecraft track gauge" could have told you that.

still too small. the head of player clips through roof

still too small. the head of player clips through roof

still an extremely minor issue

still too small. the head of player clips through roof

hows this for height?

The player clipping is more of a rider position issue than a scale issue, the train is normally short, that doesn't play well when it's scaled down to 750 mm.

That is a valid issue though, so I'll see if I can fix the rider position for the next update.