Ok fellas...318 help needed , Mpg , reliability and enough power ***for a big boat !!!

@rumblefish360 must have read my mind. I am thinking that if you go for a bit of performance and the sound of performance, good mileage will be a pipe dream. I guess it depends on what your definition of 'decent' is. Build it the way you want, and just accept the mileage.
Thanks brother. I agree with the bold I added to your reply above.
Just what is decent power. Mileage?
Hence my extra small cam size warning.
A cam change that will just simply help increase the rpm in which you are cruising at is the only kind of cam I’d be looking at.

Consider a good spread bore.
I like that idea. TQ only for me. The OP, should he decide for a TQ should source an electric choke TQ. It has the small primary @ 1.38.