The in and out movement of the '49 striker is accommodated by the movement of the threaded bars on the inside of the cab which the striker screws are threaded into. The countersunk screws don't have anything to do with the adjustment.
Take your strikers off and find out why the threaded bars aren't moving in and out.
Carl

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission