Tony,
The little lock-nut jack-screw that I speak of is INSIDE the engine, up near the oil pump shaft.
It locks the pump housing into the block. You are merely removing the distributor so when you reinstall the pump, you won't hang up on the tang of the distributor shaft.
I have enclosed a link to a picture. I hope this is what your setup looks like, or I might be all wet.
You can see the screw and locknut in the picture.
http://chevy.tocmp.com/1929_54chevyparts/01/133.HTM Stuart
