Here’s the GM listing for BBC flywheels:
https://www.chevrolet.com/performanc...els-flexplates

Not sure if that is 100% correct.

This is the same thing that my older GMPP catalog shows :
Thius is from the Pace Performance web site. Dont know why I cant seem to actually put a link to the page

14096987 - CPP Big Block Chevy 14" Gen VI Manual Transmission Flywheel 1991-On - For Use With CPP 454 & 502 Crate Engines With Forged Cranks

SKU: 14096987

Description

14" flywheel for 11" clutch.This flywheel is specifically balanced for GMPP 454 and 502 Crate engines with forged steel crankshafts.Do not use on production 454 engines with cast crankshafts.

The first number at the GMPP link is coming up as a smallblock flywheel in the PDF catalogs.
Snip out of 2018 (top) and 2023 (bottom) Chevrolet Performance catalog, flywheels offered then and now.

and none of these specify cast or forged cranks..

I wonder why the Pace Performance site does ? They are one of the biggest GMPP dealers. Ill do some more research tomorrow Unless GM superceded them to all being the same but that would be unusual for them to do without changing a part number.

Its interesting. The truth is out there! Lol

Bill K is correct:
Mk 4 external : 33 ounch inch
gen V or 6 with cast crank : 41.7 ounce inch
gen V/ 6 steel crank: 42.5

in your opinion, is it going to cause a problem if I run the flywheel for the cast crank on my forged crank engine?

If I say its ok and it hurts your engine is it going to be my fault After all its always the machine shop's fault Its kind of hard to feel a vibration in a boat compared to a car. I dont know of anyone who has run it like that long term so its very hard to say. Dont know if an oil analysis would tell you anything or not.

I’ll bet $10 .8 ounce of jb weld will stay put. he he