As for the action screw hole, it sounds like you have the skills to set the action on the drill press table and square it up with the largest drill bit that will go into the hole easily. Secure the action in place, remove the drill bit, and replace it In the chuck with a 1/4x28 starter tap, run it into the hole and rotate the chuck by hand, chasing the threads. This has worked for me in various different applications. If for any reason this doesn't work, your next best option is to rebore and move up one thread size.

I would "NOT" drill a hole in the top of the action! :-((