I was replacing distributor after getting engine to TDC and used a long screw driver to move the oil pump stem in the direction of #1. The stem turns quite easy and there is even some play from side to side. Is that normal?
As jeff66 just stated... yes, the oil pump shaft is very easy to turn with a screwdriver. And yes, the oil pump shaft does wobble.
Try to remember that as you are installing the distributor into the intake manifold, the distributor gear will begin to mesh with the cam gear... and the rotor will begin to turn as the distributor is lowered. The slot in the distributor gear is going to insert into the slot on the oil pump while the distributor is still being lowered with the gears meshing... so you have to find the right spot to position the slot in the oil pump shaft to catch the tab while the rotor is still turning. NOTE: IIRC, the rotor will spin in a clockwise direction as the distributor gear meshes with the cam gear during installation. You need to take this into account as you begin to install the distributor.
I found this trick helps.
While the distributor is still out of the engine, place a piece of blue painters tape on the top of your rotor and draw a line that would correspond the the position of the oil pump tab in the distributor gear.
Next, while still holding the distributor... place the rotor so it simulates where it would be pointing at the #1 cap terminal (when installed in the engine) and note the position of the line you drew on the top of the rotor.
Now, position the slot in the oil pump shaft so it is about 1/8 of a turn back/counterclockwise from the line on the blue tape - when the rotor would be pointing to the #1 cap terminal.
Install the distributor. You may have to "fine tune" the oil pump shaft's slot position so that everything lines up during the distributor installation.