If your brake arm is smashing your brake light switch lever against the floorboard, you likely have a cab-to-frame alignment issue which you need to investigate. There is an internal stop inside of the master cylinder which dictates the position of the piston at rest (no brakes applied). There is an adjustable pushrod which when adjusted, dictates the distance between the firewall and the brake arm. That bumper on your brake arm may be adversely altering the action of the piston inside of the master cylinder.

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