All of the above answers are correct especially if you do not have a distributor in the engine. If you are swapping a rebuilt one for the old one that is allready in the engine, why not just remove the cap and rotate the engine so that the rotor is pointing to a particular spot such as the fender or engine block, and then remove the distributor and replace in the exact position. You don't have to know TDC or exhaust/intake valve location, IF the engine was running before taking out the distributor. You will have to fine tune the engine after installation.
