First, what Edelbrock was that? I love their Carbs on boats. Boats are a different world then street motors and they are built tough and simple and easy to fix a rich or lean.
Second, an alpha drive you don't want anything stupid. Alphas behind BB's were a big mistake for Mercruiser even for their 330 BBC and is the reason the Bravo came out.
Third, what comes around goes around. Eagle's name has gone to $hit over the years and Scat has become more desired. Figure that out.
Forth, this is what I did 6 years ago an I run the piss out of it in a heavy 19' Nova.

1980-90, 14015445 (7.4) 454 - 4 Bolt Main Big Block

Dipped And Honed The Decks And Cylinders Cut .060 Over

Block Was Detailed With All Casting Debris Removed

Scat 9000 Crank 4.25, 496 Stroker - cut .020 under

Scat 26385716 - 6.385 in. Connecting Rods - Floating Pins -I Beam Forged 4340 steel

Howards Cams 120255-12 - Max Torque Retrofit Hydraulic Roller Camshafts, Hydraulic Roller Tappet, Advertised Duration 288/294, Lift .585/.610, 112 L/S

Howards Valve Springs 98636 (recomended) - 130# / 330#

Comp 780-16 Spring Retainers

Cloyes Gear 9-203 - Cloyes Wear Plate, .031 in. Thick

CCA-205 Cam Button

Maxspeeding Hydraulic Retrofit Roller Lifters

Probe 496 Dome Top +18.0cc, .060 - SRS - PHV Series Piston Set

Cloyes True Double Roller Timing Chain

Mahle - 4.310 Plasma Moly Coated Piston Rings

Melling 10778C (Anti-Cavitation) Oil Pump

Melling HV Oil Pump Shaft

New Solid Harmonic Balancer

Rotating Assembly Fully Balanced

Trick Flow Chromoly Pushrods TFS-21417800-8

Heads 6272990 / Date Codes 1/25/81 and 1/29/81 / Open / 118cc / 3 Angle Valve / porting services - Mullen Race Engine Cylinder Heads, Carson, Calif

Summit Racing / SUM-V8030-8 Stainless Steel Valves 1.880 in.

Summit Racing / SUM-V8022-8 Stainless Steel Valves 2.190 in.

Chevrolet Performance Head Bolt Kits 12367779

ARP 1.90 Rocker Studs

Norris S/S 1.7 Roller Rockers

EDELBROCK BBC R2 AIRGAP INTAKE

Pro Comp 2752 Fuel Pump

MSD Ignition

Pro Comp Distributor

Super Stock Coil

8mm Accel Hi Performance Wires

New Single Wire Alternator

Mini (gear reduction and fully marine) 3HP Starter

Edelbrock 800 Carburetor

12" Aluminum, Oval Air Cleaner With K&N Filter

Brass Freeze Plugs

Stainless Steel Bolt Set

4" Stainless Steel "Tall" Risers

496 MerCruiser Exhaust Manifolds

Sherwood Motor Mounted Raw Water Pump

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Clevite 77 Cam Bearings

Federal-Mogal 4400 M20 Main Bearings

King Engine Rod Bearings CR 808 HPN 020


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Edelbrock 7202 Intakes Gasket Set

Trick Flow Gasket Set

Fel Pro Q2904 Rear Main Seal

Fel Pro 1804 Oil pan gasket

Fel-17040 Head Gaskets

well not sure on how much power you are looking to make, But I have run several non forged setups, beat the hell out of them, never had a issue due to them, at power level 90% of marine engines are, put in a set of ARP rod bolts, make sure rods are round, crank good, set bearing clearances and roll on..buts thats me..

Sounds like someone was trying to go for the gusto with a peanut motor.
A forged mag crank 7/16 rods and a set of trw minidome ls6 replacement pistons should all balance properly and still give you the right compression if you have 118cc or so chambers.
May have to buy a new flywheel.
Odds are , it will offer less vibration at mid rpm than before also....

You may have to buy a complete shortblock to get these goodies we speak of though, but will save some hassle