Ok, I am just speculating here but what would you do? I have no budget for this, its the speed bug talking.
I have a 489 stoker with about 500HP.
Large oval ported heads with bigger valves.
Forged internals
RMbuilder Cam, Isky springs, Moral lifters, you get the idea.
Holley MPI, 1000cfm TB, 42lb injectors, wideband 02, ram air
EMI exhaust with long risers
Flat top pistons, -3cc, 110 chambers, with 8.9 compresion

Proposal #1
Bore out to 496 with dome pistons, aluminum large oval heads (edelbrock E bare heads with a little work), raise compresion to 9.5 or better.

Proposal #2
Swap out most of the parts to a 502 and make a 540. Use GM Rec heads with a little port work. Raise compresion a little and have RMbuilder grind a new cam.

Damn speed bug, my wifes not going to like this either way !!!!

Nice build. Sounds like you could get a cheap 100 hp with forced induction.
Don't forget the whipple option. Pistons gaskets and 5k?
B&M 250, faster than a compete rebuild. You should be able to pop near 700 hp if you invest in what you have. I guess you have to decide if you want to run the canned gas at $7 a gallon with the high compression though. I have heard that some drives can be tweeked depending on what you have for 5 - 10 mph. Look at the whole boat when you are at the point of speed withdrawls.
First I would look into square port heads 990's or 780's are redily available andd cheap.
Lay out the details of you current set up and we will gladly spend your $.

Yea, thought about supercharger, the snout would hit my hatch. I have wrap around seating, that brings up other issues. I have thought about a twin turbo, big turbo/low boost setup. If I did a 540 I would find a used 502 block, but getting harder to find. If I had 600HP that would make me happy for a while. I need to freshen up the drive, the stock bravo has been holding up well. I want to stay with pump gas, prefferably 89, the fuel sucks, that may be why I am down 2MPH from last year.

Maybe sell it and buy a boat with a faster hull? Many times folks regret to spending all of the time and money to not gain much. It may be pretty hard on drives also. The wife REALLY won't like that! Do some shopping before you sink a bunch into this one. You may still make the decision to build a motor, but then again you may not. Just the right newer boat could make both of you happy.

Well, maybe good advice. But we like the boat, way more room than others. I have raised the x up 3" and the boat looks like new. Just ask the guys here that boat with me. It is really fast for what it is, it runs 74 in ideal conditions. I am not planning on selling it, I will keep this boat and collect others before I do that. It responds well to HP I have always gained speed. I will not be sinking a bunch of money on this. I may not do anything,

I talked to RMbuilder a few days ago. He seemed to think I could get 620HP out of my engine. I would need AFR heads, new cam and bump up comp. I could do this project in two steps, the heads one year, then the new pistons and cam the next. That may be the best option unless I find a smokin hot deal on a 502 block and rec port heads.

find a high hour 502 mag complete that you can steal. turn it into a nice clean 9 to 1 injected 540 and quit while youre ahead. you'll see 550 - 560 without breaking a sweat, reasonable revs, no fuel complications , no magic, and very very good reliability.

Yea, I am already at 520HP, I would like to gain 100HP. A 540 setup would be a great, I could reuse most of the parts out of the 489. Should be able to get 600+ HP pretty easy.

For reference I got 695hp out of my pump gas 489" pretty easily.

Brodix supercat heads tweaked by my head guy is where most the power came from. No need to go to 540" for 600hp.

Procharger would get you there and then some pretty easily too.

yes it would as would any number of other combinations but the 540 is understressed at that, lower revving and without any of the complications of these procharger deals. 540 stuff is cheap off the shelf and well proven. i would suggest that the dollars per HP ratio for a 540 would be half of what a procharged deal would be and last twice as long... money and time that can be spent on far more important things like alchohol and women.