Bring the engine to #1 TDC, turn with a breaker bar on the crankbolt if necessary.
Pull the distributor cap off, and mark on the distributor housing with a paint pen or something equivalent, where the rotor tip is pointed.
Now mark the position of your distributor housing in relationship to the intake manifold.
If you have a vacuum advance unit on your distributor, make a line on the valve cover where the vac. adv is pointed.
Disconnect the wiring, and the dist clamp and remove the dist. When removing the dist. notice the rotor will turn counter clockwise as you lift it out of the engine. Make a mental note of how much it turns...maybe 45* or so. You will need to copy this amount of CC rotation when you put it back in.
If you have a priming tool, that is great, I have made one out of an old distributor, and ground the tip of the dist shaft down to fit into a drill. This works real well as the housing supports the shaft while turning.
So spin your primer tool, you'll feel when you get oil pressure as the drill will slow down from the pressurized load on the system. Remove the tool, and set distributor back in the engine. It probably wont seat on the manifold due to the oil pump shaft and the distributor shaft not lining up. If so, remove the dist. and using a large screwdriver move the oil pump shaft to the position to line up with the dist. shaft, and try again. When you get it right it should seat on the block and the line you made to the valve cover should line up with your vac. advance unit, and your rotor should line up with the mark you made on the housing.
If they don't line up, lift up the housing about 1" and rotate the rotor to get it to line up when the housing is seated. this may take a few tries.
When you get them to line up, be sure to time the engine with a timing light.