Ed,
you gain kind of nothing to contact the motor manufacturers... the knowlage is found here
they only make motors, we use them.
I like the high performance geard setups, as I can use a lighter motor and still have massive power. I think a Hacker B50 geard to swing a "large" prop, say 15x10-12 would do best in your little P51. check aircraft-world.com for prices.