Are you referring to the instrument panel or dash panel. If is the dash panel I think they use 1/4" x 1/2" long oval head slotted screws. I am a 28/29 person, so I could be wrong for a 30/31 dash screws.
Rusty Nelson
Rusty you are correct. dash rail 1/4 20 oval head on the face and one 1/4 20 slotted stove bolt at each end to the door posts, instrument panel 10-32 oval head
What Rusty says in post#3. The oval head dash panel screws, not the instrument panel screws are 1/4 X 20 threads per inch. I'm not sure about length but probably no over 3/4 inch long.
Rusty you are correct. dash rail 1/4 20 oval head on the face and one 1/4 20 slotted stove bolt at each end to the door posts, instrument panel 10-32 oval head
All the original cars I've seen also used the oval head screws at the ends of the panel. This is why the end tabs are always distorted and need to be straightened during restoration.