Jim - Welcome to Stovebolt!
The part you've identified has been a frequent topic in the Swap Meet section in the past as they are usually discovered to be missing when folks get to working on their parking brakes. Unfortunately, once those Swap Meet ads are resolved they get deleted so, we'll need to provide a little more info here to try an answer your questions.
Per the Master Parts Books, the Parts Group 5.150 extension for your 1950 Huck brake 1/2 ton is identified as GM# 475481 - Left (7-1/16" OL) and GM# 475482 - Right (7-1/16" OL). They are side specific, so you will need to clearly indicate which one (or both) you need when you post an actual "Swap Meet Ad" in our
Truck Parts Wanted forum.
I've attached a screenshot from a Chevy Master Parts Book showing the extensive application list of vehicles that used the Huck brakes from 1936-50, as they are all the same part. Should make it easier to find the part you need as there are many more sources than just the pickups.
Looking forward to seeing your ad and being abke to help you find the part(s).
