I thought I saw this post before but here is a reply. It seems that in 1950 you would still have the Huck brakes on the 1/2 Ton. They have adjusters on the wheel cylinder. According to this page in the manual,
Shop Manual -Brakes
your brakes would not have the conical springs.

Also, you need a parking brake spreader lever on each side.

1951 GMC 1 Ton Flatbed -- It is finally on the road and what a great time I have driving it!
1951 1 Ton Completed

My Chevy Master 4 Door is on the Road!