1970 Arm Rest Screws

[cericd]

Anybody know what size screws I need to attach the arm rests to my doors. It's a 1970 C/10 with the base model metal door panels. I took them off a while back and misplaced two of the screws. I tried to thread one of my original screws into one of those nut and bolt size finder dodads but it didn't fit anything. It would catch about 2 threads in the 1/4-28 but that's it. It wouldn't thread into the 1/4-20 at all.

These are the arm rests and original screw I'm talking about.