Distributor Locking Screw, HELP!

[MurphyJ]

I replaced the head on my engine and after the distributor was placed down in position I attempted to install the distributor locking screw and find that the screw will not turn or screw all the way in to reach the distributor base. The screw appears to be tapered and the hole in the head's threads appear to be tapered as well. I'm stumped to say the least. Have other Model A owners experienced the same problem ? Any tips, suggestions, comments will be of great help. I thank you.