Ultimate 4.3 Mercruiser Engine Build

I want to build the ultimate 4.3 Mercruiser.
Please give me advice this is what i have come up with so far.

Vortec heads with roller rockers.
Non balance shaft block. ( I have heard on the internet that the non balance shaft block is better for performance. Can anyone tell me why?
Edelbrock 2114 Manifold with 4 barrel marine carb.
Hi-tek stainless exhaust manifold.
Cold air induction.
any other suggestions?

I dont want to put a v8 in there as the boat/leg ratio is set up for a v6 1 and I already have s/s manifolds etc.

I want about 250hp is this possible?

Re: Ultimate 4.3 Mercruiser Engine Build

Anything is possible, just like anything can be fixed...for a price.

For instance, you might find that XXX HP can be had by a fairly radical cam that requires you to wind the engine way past what the drive is rated for...and the engine will probably end up being a dog everywhere else.

As far as the bolt-ons go - the smaller the engine displacement, the less of a gain you're likely to see from a given part. So the intake, carb, and manifolds on your engine aren't going to give you the same gains you'd see using similar parts on a 350.

It really comes down to how sure you are about not wanting to go the V-8 route. You might find that you can sell your drive and locate a properly geared replacement and at least break even on the deal, sell the performance parts you have so far, and build a 383.

Maybe the best place to start is why you're doing the build, what you want to get out of it, and how long you want the engine to realistically live. Are you trying to get 250 HP at the flywheel or at the prop?

If you are set on the V-6, the next logical step is probably to talk to a custom cam grinder and get their input. Just keep in mind that power numbers are meaningless if they don't specify RPM.