I just torn down what was supposed to be a 1989 454 mag.
I found it DOES has 4 bolt mains, but it also has peanut port heads.
Is this normal? Is it actually a MAG?
Also did the MAG engines come with an Edelbrock Performer 2.0 intake stock?

Are these heads worth using or should I reccomend the owner start looking for better heads?

330 HP engines had 4 bolt mains and small heads.

So it won't have any of the good forged parts?

The Mag has a steel crank and forged pistons. I thought it came with rectangular heads.
Edelbrock Performer Nope not stock.
Change heads - depends on what your goals and how deep your pockets are
I have a fresh set of 781 large ovals. PM me if you are interested.

Nope, not a true 454Mag.
By chance was it hooked to an Alpha drive?
There were a couple of years, 87 & 88 I think, that they called a 330HP/454 a Mag when it was hooked to an Alpha.
Strange, I know...
Anyway, you likely have a 330HP/7.4 with flat top pistons, 3/8 bolt rods, cast crank, and peanut port heads.
Far from a 365HP/454Mag with rec port heads and forged stuff in the bottom.

Would the 781s make much difference?
The guy was planning a carb, cam, intake change and looking to be around 450 hp.
Now what is it going to take?
Things to keep in mind..... HE WILL BEAT THIS MOTOR. It will be reving at least 4500 if the boat is in motion. He was planning to rev it 5500ish WOT. With the 330 parts hold up?

454 Mag had rectangle port heads. Intakes are by Winters, same as forged the '67 435 hp tri-power vette. I have (2) original intakes and carbs with shrouds for '89 454 Mags in my storage area if you are interested in them. Redline was 5000 r.p.m.

literally building two of these motors now....

Same steel crank, 4 bolt main, forged pistion, small heads....

Installed Dart heads, "Comp Cams Extreme Marine" roller kit, roller rockers, (547 lift cam), dual plane air gap intake, and Elderbrock 750 carb gets you to 440 hp, and it runs NICE. Hits a good lick, but still VERY drivable.....

PM me if you want info, I have one off the dyno, one going on this week.....

Lots of guys build 400-450 HP engines from 330hp/454s, but it does take some work.
New heads, cam, pistons, balance rotating assembly, intake, carb, exhaust.
Most say the engine should be run under 5000rpm with the cast crank and small rods.

wt
I f you have the serial number off the tag by the starter I can run it through midas and tell you what it is for sure but it appears that you have a 330 hp. Ed