Orig post indicates possibly you intentionally purchased a gen 6 flywheel for a gen 4 or your wondering if someone put the wrong flywheel on your motor prior . Or im tired . I would start from scratch .and yes 2 piece gen 4 witness mark is not round like one on left .cleaner one gen 4 for shore. I know the auto flexplates are different balance gen 4 cast forged or 502 gen4 3 different balance. Not sure about mercs man trans gen4 flywheels though . But i would check before slapping something on there and getting a teeth rattling 2000rpm vibration

I know you dont have a clutch plate on that thing and used to be able to get new ring gears for $40.00 and maybe you have a welder buddy just sayin

sounds like you bought a gen 6 motor to replace dead gen 4. then you got a flywheel for it. they are both 2 piece seal early flywheels. don't use on gen 6 engine bad vibration...http://www.jegs.com/i/GM+Performance...96987/10002/-1 or post what you need in the wanted section. i only have one spare and i am not sure i don't need it yet.

Yes, you guys are right. I got a gen 6 engine to replace a water infested mk 4. I knew the flywheels were different
But was sold the wrong one by mistake. I'll just scavenge my other gen 6 motor for now and order that one from jegs when I start rebuilding the other motor in a couple weeks....

Thanks as always guys

One more detail. Cast and forged cranks take different flywheels.

I think I have a Gen 6 fly wheel off a mag 502, casted in 805. And I just so happen to need a mark 4. Maybe we can work something out.