My best guess, car not truck. The MC looks different.
The rear wheel cylinder looks like this:http://www.classicparts.com/1947-52-Wheel-Cylinder/productinfo/71-141/#.VNOb7kfF9mM
The front wheel cylinder looks like this:http://www.classicparts.com/1947-50-Wheel-Cylinder-Front-EW3406/productinfo/71-105/#.VNOchEfF9mM
And the Master Cylinder(MC) looks like this:http://www.classicparts.com/1947-50-Master-Cylinder-1_2-Ton/productinfo/71-205/#.VNOc10fF9mM
New Brake shoes look like this:http://www.classicparts.com/1941-50-Brake-Shoes-Front-Rear/productinfo/71-011/#.VNOdGEfF9mM
And the front drums if needed look like this:http://www.classicparts.com/1941-50-Brake-Drums-Front-1_2-Ton/productinfo/71-408/#.VNOdUEfF9mM
While the rear look like this:http://www.classicparts.com/1941-50-Brake-Drums-Rear-1_2-Ton/productinfo/71-409/#.VNOdl0fF9mM
But you can repair a lot of the wheel cylinders with these: Front http://www.classicparts.com/1947-52...3_4-Ton/productinfo/71-171/#.VNOd30fF9mM
and rear http://www.classicparts.com/1947-50-Wheel-Cylinder-Kit-Rear-1_2-Ton/productinfo/71-181/#.VNOeFUfF9mM
You might use this to fix the MC: http://www.classicparts.com/1941-50-Master-Cylinder-Kit-1_2-Ton/productinfo/71-255/#.VNOeTEfF9mM
You can get these: http://www.classicparts.com/1947-52-Huck-Brake-Anchor-Pin-Lock-Clip/productinfo/71-514/#.VNOemkfF9mM
And you might find that pin in the "Parts for sale" forum. There are other vendors for the parts. This vendor has good pictures to help you as you try to find what you need. Just ask for "Huck" brake parts. I don't know if any one is making the pin so look at the parts for sale.

Steve H