Once the balancer has been installed and run it can't be returned. Now it's a "used" part. Would you be willing to buy somebody else's mistake that's being sold as a "new" item by a parts store? Now it's time to make the rest of the pulley system match the balancer you have. There are two different timing mark positions for small block engines, depending on the year of manufacture. Early engines have the TDC mark at about the 2:00 position, looking at the front of the engine, and later ones have the TDC mark at 12:00. The balancer and the timing cover need to match up. Short shaft water pump engines almost always need the balancer and timing cover with the 2:00 timing mark.

There's a very well-established method of finding true top dead center by putting a fixture into the #1 spark plug hole and carefully turning the engine in both directions until the piston touches the stop fixture. TDC is midway between those positions.
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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