Jeff,
I sure am learning a lot about '41 trucks!. A hydraulic brake switch...pretty space age for that old beast.
I'm not sure on this, but as long as you only lost fluid within the master cylinder proper, I would bet you could refill it, and by slowly pumping the pedal, get it to self bleed.
I think you want DOT 3 or 4 brake fluid. DON'T use DOT 5 fluid.
Sometimes, you can fill the reservoir at night, and by the next day, it will have 'bubbled' itself to some pedal.
Try the fill and pump routine first, you might get lucky.
Fill it nearly to the top, but lay the cap back on...sometimes they 'spit' at you.
Stuart
