What Harmonic Balancer is this?

OK, here is what's confusing, the block has casting numbers of a 71' 383, Was there ever an externally balanced 383?

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Looks like you took some nice pictures of the engine on the stand. Did you happen to snap a picture of the crankshaft? If so you can go back and look at it to confirm if it is a cast crank or a steel crank. Seems like you have one of the first cast crank 383 engines but you might have the proof on your hard drive.