Along the lines of what "Zener424" suggests, a quick way to see if the rotor is far off is to remove #1 spark plug, take off the distributor's top cap w/coil wire so that you can observe the rotor as it turns, stand on the passenger's side, and hold your right thumb over the open spark plug hole. Leave the plastic distributor body in place. Reach across the top of the engine with your left arm and push down on the start rod with your left hand. Be sure the ignition key is OFF to avoid unwanted spark arcing and the transmission is neutral! As the engine spins and the rotor's brass tang approaches #1 on the plastic distributor body (at the 4:00 O'clock position), the cylinder pressure should push your thumb off the spark plug hole. That's TDC. If it doesn't force your thumb off with a "whoosh!" at this position, but instead at the 10:00 O'clock position, that means the rotor is set 180 degree's opposite. This quick test will tell you if you are in the ballpark for initial ignition timing setting.
If the rotor is close to #1 at TDC using this test, you can fine tune the rotor's setting using the timing pin and hand crank. Put the spark lever all the way up, remove the timing pin, reverse it and put it back into the hole, and while putting inward pressure on the pin, slowly hand crank the engine until you feel the pin drop into the fiber timing gear's detent hole. It's subtle, so don't expect a big drop. You'll be prepared for this position because the rotor's tang will be approaching the #1 terminal inside the distributor body. (The rotor will turn counter-clockwise) Once the pin drops in, stop hand cranking and reverse the pin, tightening it. Remove the rotor, loosen the distributor's cam set screw, and replace the rotor. Position the rotor's tang by rotating the rotor so that its TRAILING edge is just past the #1 terminal of the distributor body. This is the correct initial setting. Remove the rotor and tighten the set screw. Put everything back together again and start the engine. You can tweak the timing from here for your needs: either a slow idle and less power by retarding the initial timing, or for more power, but a less smooth idle by slightly advance the initial setting.
Marshall