When i bought the boat i was told it was stock 455.. The compression is 155 across the board. it does 55mph. Has an edelbrok performer intake.
Depending on what all else you plan, your best bet would be to stick with 112° lobe separation and mild lift with longest possible duration.
I really like the Comp Cams Xtreme Marine XM270H for situations such as yours. It's a proven off the shelf stick with a pretty good track record.
Hope that helps.
GT
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