There is a seal in the timing chain cover. You access it from the inside of the cover (sounds like this is an unfortunate fact if you are ready to reinstall). It is a rope type seal that is held in place by a retainer ring, similar to a "real" seal.
Oh yeah, this thing seals on the Harmonic Balancer, NOT the crankshaft. If the balancer is not on yet, oil will run out even if the seal is good.
If the seal does not hold oil with the balancer installed, I would replace it. With the timing chain cover removed, you can knock the retainer out with a punch and hammer (careful not to damage it, only takes a few light taps). Remove & replace the rope seal and reinstall the cover. This operation will require a timing chain gasket kit and the removal of fuel pump, distributor, radiator hoses, alternator, p/s if any and the front two oil pan bolts. If you are careful, the oil pan gasket will remain in place and you can seal with some sealant when replacing the timing chain cover. (Just did this on Ole Yeller with my son.)
Good Luck, Brad.