Well... my suggestion would be, before getting into the weeds of deck heights and what roller cam you need to stick in it, figure out what you have, what you are trying to do, and what sort of budget you are trying to work with. I mean 600hp is cool and all... but if you are rolling with log exhaust in a daycruiser, the reality is you won't use the power and quite frankly, will have a hard time making it with super restrictive exhaust. So what you have to work with kinda really sets the stage for what you can do (with what you have) or how much you are going to end up spending (if what you have is un-usable to achieve your goals). Hp is cool... but the reality is, what are you trying to get out of the boat... figure that out and then you will know what sort of hp you are going to need to get there. You may find that to meet your performance goal... 500hp will do it... or your goal may be such that 600 won't get you there... the performance goal dictates the horsepower you are going to need to build for.

Based on your photo... you have large chamber peanut port heads... 600hp on pump gas (or even race gas) is not going to happen... you literally cannot flow enough air to support that much hp. Not saying they are junk... I've built a few 468's with those heads fluffed up... Not crazy hydraulic flat cam... 9:1 cr... With manifold thru transom exhaust... engine done up nice and dyno'ed at 456hp@5000 & 553tq@3800. Which pushed a 21' Ultra 67mph. Just saying that already, you are going to be much deeper than some machining and a few bolt on parts to anywhere near 600hp.

So I would suggest figuring out what your goals with the boat are... what you have to start with... how much your willing to put into it... and then you can get a good idea of what it's going to take both as far as a build, and as far as costs... not just engine, but ancilery parts and mods.