Volvo Penta 5.7Gi-e upgrade help needed

I have a VP 5.7 gi in an 04 Caravelle Interceptor 212. I am chomping at the bit to get more power out of this motor. The boat currently runs a strong 59 mph on gps at 5000rpm. I am in the process of adding a piggyback computer to allow adjustments after my modifications are complete. I am not sure how much power I am looking for but I would love 65-70mph. I have a few questions for anybody that might be able to help. First off I am planning on doing heads, roller rockers, and a cam. I am debating about cast or aluminum heads, I live in Wisconsin and the boat will never see saltwater. I like the thought of less weight but I have been told that aluminum wont hold up to marine applications. Is the any truth to that? any suggestions on heads? Next would be the cam, I have read almost all of the posts on here and realized i was not nearly as smart as i once thought. I have been told that I cannot go too extreme with the cam due to the knock sensors. Is there any recomendations for a cam? I have read the previous post about the GM performance and Crane cams, I do pull tubers but I am ideally looking for top end. I am planning on doing the beehives valve springs in the process. I only want to pull the motor out 1 time. I have 2 other questions, I pulled the throttle body and it measures 74mm, is that sufficient to handle 375hp? I am also trying to find an aftermarket fuel pressure regulator but i have not had any luck. Thank you in advance for any input you may have. No I do not have room for a big block, already looked into that also.

Thank you!