Mercruiser part numbers for all the fist engine serial number runs from day one. The mag and HO used the exact same crank part number. And in Volvo school we all went over this in 2002. I will try to find my class material and post a pic of that. Here is the Merc part numbers for HO and MAG Cranks both the same from day one - check it all out in the links below. Like I said maybe if even that 500 went out as forged cranks for the HO only but actually maybe 200 if I had to really guess really went out as forged cranks.

MerCruiser 496 Mag (H.O. Model) Block-crankshaft, Oil Pump, & Front Cover Parts

HO 496 link ^^^^^^^^^^^^^^^ for crank part number as shown in number 3

And the MAG crank numbers below link number 3 they are exactly the same from day one. Mag 375 hp vs HO 425. I would bet not many were forged cranks from GM period. Merc got these as long blocks and the same with Volvo - I will post my class material.

http://www.marineengine.com/parts/me...nd-front-cover

And here is the first and foremost the GM 496 that the race boats as well. This is GM first run brochures that came out way back for the intro of their HP3 496 that used MEFI 4 and cast cranks as well. Here is the proof in the GM 525 plus hp engines. Read the specs ---- CAST CRANK

Myself personally never seen a forged crank in a 496 ever but I have heard of TWO people swear that theirs was a forged crank. One was up here on OSO. https://cimg5.ibsrv.net/gimg/www.off...a78486d2f9.jpg

GM HP3 specs here from the brochure I have --- its the first ones out to the public many years ago.https://cimg4.ibsrv.net/gimg/www.off...0aa8948947.jpg

you guys are awesome!