just for pleasure of taking engine! Lets say you wanna have at least 600 hp, but mainly 650-700 hp...
we all know a 500 efi with a bolt on whipple runs around those number between 650-700, not sure about real numbers...
i also remember it is not overthinking a 540 can push 650 ish reliable hp
gm makes 620 hp and or 720 hp on race gas from 572 cubic inches. And i remember someone on the board had 632's cubic inches but cant remenber how many hp he was pushing.

So many ways to play around those hp numbers

if you were to choose a recipe, what way would you choose? No replacement for displacement? Or blower? , keeping in mind dock friendly, and stay far from reversion, and cost of maintenance!

While we are at it, carbed? Or injected? And why?

Blowers. For 600-700 N/A is fine. Above that I'd go blowers. Also depends what you're starting with.

I am having a 540 built that should be about 650 HP. I hope that the NA motor will be more drive friendly. If I need more, I can Whipple it. Bottom end built to stand 1000 HP and that much torque. 650 should push 29 Fountain 80ish. Will know by spring or on a warm day this winter. Holley EFI instead of carbs.

I currently run a N/A 548 in my 30ft boat and it is really easy to drive but I have no space for pulleys to install a blower. I run at high altitude so a blower would actually help me out a lot but a boat at sea level will have plenty of air. I come from drag racing and was expecting to see more of the big cubic inch 632's and even larger N/A motors in these big boats. Pretty easy to get 900-1000 HP these days with a single carb on pump gas with a 632.

we ran a clone 500HP with a MS3 procharger with both 2 different carb setups, one in box(hated it) but ran fine hard to service, EFI, and back to blowthru carb, ran engine for almost 5 years, with blow thru carb ran great on 5-6 psi

A well built 502 with an 8-71 blower, small cam and fuel injection. It will idle like a minivan and make 700hp easily and reliably. If NA is in order, 555 or 565CI with the Holley fuel injection. It will take a little more cam than the blower motor and would stand more chance of being a little grumpy around the docks and more possibility of reversion.

I've got a pair of 540's making 675 with Dominators that I've been running for four years, (about 500 hrs). I spent a lot of money and bought the best of everything. They've been trouble free other than a rocker arm failure this year which the manufacturer ponied up with two new sets. Fortunately nothing else got jacked when the rocker broke. While the Dominators have performed well I'd be willing to give up a few HP for the fuel economy of EFI.

what rocker arms if you don't mind me asking?

Scorpions. They sent two sets without asking for the old rockers to be returned. All they asked for was a pic of the broken rocker which I emailed to them.

Carbed roots blowers for that HP level. They look and sound fantastic. Your power band is as wide as the country side and everything is kept simple. We had Edddie Young build/tune one and it idles all day and fires with a quick turn of the ignition switch.