A few people have posted inquiries in the past wanting more power from their boats. PleasureCraft states that 50 HP can be gained by installing the GT-40 heads on non-GT-40 351s. I believe these heads also work on 302s.
The post below came from correctcraftfan:
PCM now has new Ford 302, 351, 351 HO base and complete engines now available through your local dealer. These are brand new Ford Marine OEM engines ready for instalation in your boat. We also have GT-40 HO cylinder heads the will boost your standard 351's horsepower by 50+ horses!
Also Available are new Holley 4 bbl. carburetors for 302, and 351 engines for unheard of prices.
For all your Ford Marine needs see your local Correct Craft/PCM dealer and insist on genuine PCM Ford parts. If you have questions or would like a referral to your nearest dealer, please e-mail me.