This manifold looks better but it’s got a cat in it I think.

I will concur with that. With dyno headers it will be right there. The marine power manifold is the exact same manifold as imco power flow from imco. Exact. If you look at a cutout of it you will see it is like a shorty header. So not too bad of restriction but will come up 25-30 short due to that. I do plan on running it both ways on dyno as I have future plans to add lightning headers and would like to see the diffeence in headers snd manifolds. Should be fun either way. Well over 100 mph either way. If I lose 3mph from exhaust so be it

I did look at that exhaust as well but it is pricey. And my daytona has to have custom tails due to lower outlet than stock bravo. About 3” lower

Watch this. Look closely at the chart. Same exact specs on cam but using less lift and xfi lobes. It DOES have gm performance cnc heads which are good for 20 in the range hes in. My lobes will make more power than the xfi lobes.

525s make 560 in dyno trim with the different correction factor than merc uses. I’d be interested to see if your engines are any faster. The weight reduction will help.

I have a LS build also.

6.2 aluminum blocks
821 heads (ported)
Manley pro flow valves
Manley severe duty exhaust valves
Howard’s 98113 K1 spring kits
Howard’s ASA cams with 3 bolt
flat top pistons
full roller comp 1.8 rockers
mellings 10355 oil pumps
15 lb flywheels
light weight starters
Teague custom marine crossovers
dual 150 thermostats
aluminum sheet metal intakes
102 mm throttle bodies
thin head gaskets

keep us updated on this

I heard about your 67 gto death grip ride. Bad azz from what I heard. What ratio rockers you running. I may have missed in OP.

Dennis r built and just sold a while back some stroked ls3 with ls3 cnc ported heads and made like 650 hp at 6,500. Ck out his build sheet. Ran them in a 32 sunsation 88 mph.