Is there any links on internet showing data sheets/Dyno results with that combo as a comparison to the 370 hp 454 that I had to begin with
I looked into replacing the rochesters with efi carbies and estimated the cost to be $2500 per engine so if performance increase is only slight then it's not worth it

there are 1,352,751 threads on building 454s on this site.

But you need to tell us what specifically you want to accomplish and your budget....

You could easily build a 420 clone, a 420 clone with better heads... Do you want to go with a roller cam? Do you want to spin 5000 rpm or 6200 rpm?
a basic vanilla build of a stock 454 mag bottom with budget friendly EQ heads, or a little more for Big Al's heads or a lot more for some AFRs, something somewhere between a 731/ 741/500 efi roller cam setup and valvetrain, a set of used sm's or gills could get you in the neighborhood of 450-500 hp easily but each setup would be a little different.

Correct me if I'm wrong, but EQ has a direct GM replacement head. You'll be able to use your stock valves and stuff. This is not the upgraded EQ 320 others are referring to with the better flowing ports. I belive you need different diameter and length valves for them.

Ask and you shall receive. Alittle more then 454ci though

If u get different heads and staying 454-468 I'd look seriously at 265 cc oval port head. Intakes are cheap and you'll notice a big diff in power.

on a heavy boat with that size engines large oval ports like 781 or 049's and a performer RPM air gap intake might just be the ticket

wow ok guys, i will discuss all this info with my engine builder tomorrow and see what he says.

Yep. The EQ 320's, are basically the old RHS 320. They use an 11/32 valve like most Hi-Perf aftermarket heads. The GM heads use 3/8 valves. If he went to the EQ 320s, he needs all new hardware. IF he went with the replacement head, I believe all of his hardware can be transferred over. At least the valves. If the valves are good that is.

I also have an oval port head available

http://www.ebay.com/itm/MerCruiser-5...dTjkxd&vxp=mtr

Basically, its designed to be a replacment for the GM Rect ports. The intake runner is redesigned, and smaller , at 299cc. The chamber looks to be a more modern chamber design than the GM heads.

I'd want to replace the stock exhaust manifolds with something better, and a better cam than the 370HP came with. Add some roller rockers.

Stock 400/420hp 454 cam.

http://crane.carshopinc.com/product_...d/16042/132561