I would jump on that offer if I were you. Those heads and a better cam will do the trick. I wish those heads would work on a mark 4.

THE LATE MODEL 454S THAT IVE SEEN HAVE HAVE BEEN 7/16 ROD BOLTS W/CAST CRANKS BUT THEY HAVE BEEN 4 BOLT WE HAVE BUILT THESE ENGINES WITH STEEL CRANKS AND 9.00:1 PISTONS HYDRAULIC ROLLER CAMS AND MADE 460 HP EVEN WITH THE SMALL HEADS I HAVE THESE ENGINES IN SEVERAL DIFFERENT BOATS IN SOUTH FL. AND THEY REALLY WORK GREAT. ONE CUSTOMER THAT COMES TO MIND HAS A MAGNUM WITH TWO OF THEM WITH OVER 400 HOURS AND IS TICKLED WITH THE PERFORMANCE. BUT YOU NEED THESE PISTONS AND A CAM WITH 225/235 @.050 OR CLOSE TO THAT TO GET GOOD POWER LIKE YOU WANT.
SINCERELY
LAZ MESA
WWW.MESABALANCING.COM

MESA BALANCING
460 hp? Is that with 2.19 valves and no porting? What rpm?

email me about those heads, do you have the intake to match? [email protected]

I am in the process of building up my 1999 310Hp/7.4MPI.

My plan:
-L-29 Vortec Heads have been bowl ported, New stainless severe duty valves installed with new double valve springs.
-New cam with spec. 229°/229° .541/.541 114°LSA
Note this cam is custom ground to max out the stock GM lifters, push-rods, and non-adjust rockers.
-Stainless marine exhaust
-Reprogrammed ECU for the MPI.
I have been told that the MPI will hold my combo down to about 375HP @ 4600rpm and if I change to a carb it would make about 410HP @ 5000rpm.
We'll see how it goes.

I also corresponded with MadMax on this subject. He had a 1997 300HP 7.4. He changed out the peanut port heads for a set of Vortecs. Big improvement for not a lot of $$.

I'm interested in those heads. Please e-mail me @[email protected]. I will be using them on a Gen V 454