Sometimes you have to essentially do it twice. After initially setting the distributor as JD said you have to spin the engine so that the end of the distributor will "pick-up" the oil pump shaft. After priming the engine oil pump with a wood dowel and a cordless drill in a clockwise direction, GENTLY press down on the distributor while some one turns the engine in its normal rotation direction. You should feel the distributor drop down about 3/8 of an inch into the oil pump slot. After that line up the timing pointer ball with the engine on its number 1 compression stroke and "set" the distributor. If you are not familiar with mechanics enough to feel comfortable with doing this find someone in your region and have them come over to help you. This could make or break a good rebuild job. On mine after replacing the oil pump I actually had to loosen the oil distribution block on the opposite side of the engine so the oil pump would pick up oil. It had an air bubble in it and it just could not move it out. Love to see a photo of your project posted.
There is a common misconception that there are only two ways to put the distributor back in; correct and 180 off. Actually it will go in any position as long as the oil pump is lined up with the end of the distributor shaft. You don't need to turn the engine to line up the shaft.
Look into the hole with a flashlight to see where the pump slot is facing. Your distributor gears are twisted, so when you drop it in, the body is going to turn a few degrees, but the shaft will go straight down if you hold the rotor. Reach in with a large, flat tip screw driver and set the pump slot to match the distributor shaft with the rotor where you want #1 to be and put the distributor in place. If you are a little off, you can turn the rotor a bit to line it up so it will drop in the rest of the way, or pull it out again and turn the pump slot a bit more.
You can now line the distributor up so #1 lines up with the rotor, start the engine, and time it with a timing light. This works on any engine that runs the oil pump off the distributor.
This will also work to realign the distributor if the housing is off to where the vacuum advance is out of place; too close to the block or sticking out too far. A friend of mine had a '63 'vette where there is only a few degrees of swing to time the engine. Because of the tight quarters and the metal wire looms on the engine, it was imposible to set the correct advance for 6000 ft elevation until I showed him this trick.
