"or any other brushing 40 sized motor" What's a "brushing". Is that a new manufacturer?

I don't know, power specs for the Pro-36 and the GP-42 are the same. I really wonder if there's much difference.

Pro-36 is $80 GP42 is $52 I see a $28 difference

Depends what you want, all the "oomph" you can put in that plane or an excellent use of a Tower 40 that's not being used.

If its running good, I think it would be a "good" fit.