I have a custom boat, with a custom built 350. Long block is a new gm Goodwrench pre 85 350 has Volvo Penta manifolds, Edelbrock 4 brrl. 750 cfm DUI ignition bolted to a mercuismer out drive. Runs good but I want more. My auluminum prop now has a nick. It's a 19p full throttle with the 4 brrl...