I have a 1989 330hp 454. From my research, the cast pistions are the limiting factor. Detontation will cause them to frag so be conservative with timing. I've read they will not survive long above 5,000rpm

I've heard a good cast crank and 3/8" rods built up with good hardware (ex: ARP) will live at 6,000rpm.

I'm putting 781 heads (with large 1.88" exhaust) and a Performer 2.0 intake before the season starts. Don't know what it will gain me, but hoping to see ~360hp.

I ran my 1989 330HP/7.4 at 4900rpm, 36° total advance for 120hrs. The cast pistons will melt with this kind of abuse. When I tore down that engine, 2 of 8 cylinders had low compression because the rings were stuck to the pistons.
The large ovals with larger than stock valves are worth about 20HP, but with a cam change are worth a lot more.
A Performer intake is worth about 10HP over the low rise cast unit.
360HP seems like a resonable upgrade, but if you make a cam and exhaust change the engine could make over 400HP at 5000rpm.

My cousin had a pair of Merc 454cid 330hp engines modified a few years ago. He had the engines blue printed/balanced and made sure the main saddles were correct with a align hone machining process.

Two bolt mains, cast cranks, cast pistons, 3/8" rods, aftermarket dual plane hi-rise intakes, hydaulic flat tappet 218*/226* .515"/.515" on 110* lobes, 8.6 comp ratio, 32* timing, Holley 800cfm carb, large GM cast iron oval port heads that had been modified with 2.19" stainless intake valves and 1.85" exhaust valves with some bowl/pocket/short side radius porting work done to them by JimV.

On Tom Earhart's dyno they made 461hp @5100rpm and 510lbs of torque @3600rpm and stay nice and flat up to 5100rpm with DYNO tubular headers. In the boat the engines have been installed with some DRY aftermarket GIL exhausts which will lower the HP by probably about 20-35hp or so as compared with the dyno header power numbers, but he is very impressed how much better/faster his boat now runs with all the mods he has done.

I have a fresh set of 188 heads for sale {Rect,Open chamber} Inconel-stainless valves. ports cleaned up & chambers

In my 1990 251 I had Rectangle heads. Not sure if they where stock or some one added them . One went bad. Put on 049 heads. Idle improved tons. top end stayed the same. Ran good at 5k till the cast crank broke

Cam, exhaust, Performer RPM, forged pistons, ARP bolts, and a bottom end freshen/check are the next step...hopefully next winter.

Head change was due to a crack in one of the stock peanut port heads. The upgrade to the 781 w/ large valves ($100 from a friend of a friend) was a lucky upgrade.

I had a 87 Velocity with the 454Mag 330 HP strapped to an Alpha. I think it was 89 that they came out with the 365's

So would this thing make any power with forged pistons, 188 heads, a bigger cam, and a holley 800?
HE HAS exhuast upgraded and roller rockers on the old heads (if I need to swith them I will)
OR
what is this motor worth to sell all freshened up? It ran fine but "used" oil. Oil loss was a leak around the oil filter relocation housing. He decided motor was out so lets build it...........
How about a whole motor transom plate bravo 1 package with freshened motor and Bravo with 300 hrs. what is all of it worth?

EC, sounds like you got a good deal---especially, if they had the larger valves installed. Usually when larger valves are installed that the bowl area has to be enlarged a bit. If you can check the short side radius and make sure they are nice and rounded with no sharp edges or turns. Check to see if you have the hardend valve seats installed when using stainless valves or they will end up sinking within the head---it happened to us way back in the early 80's and if I remember correctly it was mostly on the exhaust side. The forged pistons and ARP rod bolts are a good idea, and if you can have the rods shot peened---might cost about $50 per set or so. Have fun.

Another question......
How would a B&M 250 work with hypereutectic pistons better rod bolts some new bearings, some balancing and some beefier bolts to hold it all together? STOCK CRANK AND HEADS
Could it make good power using the stock peanut ports (for now)?
Would it hold up provided it doesn't get revs too high..... 5000ish?