Buggered screw removal

[King Cobb]

Have a buddy I shoot skeet with who recently found a really beat up VH. We met up at lunch so he could show it to me and to use my set of screw drivers to take it apart. All was going well until we got to the screw at the bottom of the floor plate just above the triggers.

Whomever had owned it previously had buggered the heck out of the screws on this gun, and really did a number on this screw. Even with the right fitting screw, there just isn't enough surface left of the screw to get it with the screw driver anymore.

Suggestions?

The gun functions, so all in all we could just leave it assembled, but he would really like to make sure there isn't a bunch of rust in it or anything.

He also might consider replacing the screws, there are a set of 0 frame screws on ebay right now, would those work on his 1 frame or would he need to get someone to make them?