See the correction that I made to the earlier reply, it's a #14 not #12 clutch head SM screw. My 1950 uses the same size screws. The '50 is an oval head and the '54 is a flat head, both of them clutch drive.
http://www.pbase.com/dennygraham/image/133229131/large
http://www.pbase.com/dennygraham/image/133229284/large
I've never seen a nut plate in the floor board which would be required to have a 1/4-20 cap or machine screw.
DG

Last edited by Denny Graham; 03/17/2011 3:18 PM.

Denny G
Sandwich, IL