Two years ago I rebuilt a 1991 MerCruiser 454 Magnum engine. It had a Quadrajet carburetor, where I changed to slightly richer #69 primary jets/metering rods and AX secondary rods.
The intake manifold was the original "perf" 6269318, with “188” rectangle-port heads and original 3999295 forged pistons with the small dome.
I replaced the original flat tappet camshaft with a Comp Cams Marine 218/224 hydraulic roller cam and retrofit roller lifters.
The boat was a Chris-Craft 245 Limited, and with this setup it ran very well: WOT was 4800 rpm and 49 knots. The drive was a Bravo One with a 1.50 ratio and a 22” Bravo One propeller.
Now I’ve sold that boat and bought another similar Limited with the same engine, but this one has a King Cobra cone-clutch drive 😁
I’m rebuilding this engine as well, and now I’d like some advice on what I should do differently to get more power. I’ll still be using the original water-jacketed exhaust manifolds, so for example: would a Comp Cams Marine 230/236 hydraulic roller cam be a better choice than the 218/224 I used before? I do not want reversion problems.
All tips and advice are welcome.

Probably duplicate your last motor if not changing the exhaust. Edit in: that is, if your last motor had stock exhaust manifolds , and did not revert. I know nothing about King Cobra exhaust manifold design, rate of fall, etc.

I have Mercruiser stock exhaust with thru hull.