OK, so I found on the engine I wanted to swap in 1997 Buick Riviera 3800SC) Both the harmonic Balancer And the Crankshaft are broken in the keyway. the cranks "seem to come up as" the same part for either 3800SC and 3800NA. But I can't find out if the "Balancer" is the same unit. I know the flywheel if different between the 2, so....I'm "Hoping" I can get a boneyard balancer, but not sure what will fit. Help !

The NA balance only has ribs for 1 belt. The SC has two sets of ribs for two belts to run the supercharger. You will need to get an 3800SC balancer to run the supercharger. I think ZZP makes some sort of a kit that allows you to run 1 belt and maybe even the NA heads.

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Turbo 3800 E85 F23 5spd spec5
11.17@132.6

ahh, the second belt, never occurred to me. I knew the flywheel was balanced different, figured it would be like my 383 stroker where both the flywheel and balancer are both balanced different. thanks