sbafarm,
Is there a steel ball embedded in the flywheel? This is the most commonly thought of TDC, although it is probably an actual BTDC timing mark. Use the 'U' or the steel ball to get in the ballpark.
With a timing light you will set the engine to run its best regardless of any mark on the flywheel. With unlimited rotational capabilities of your new HEI, you will be able to tune to your hearts content.
I can't tell you if any mark on the flywheel is actual, true TDC of #1 piston. It isn't that important as I see it.
Stuart
