I want to make this same repair to my 1950 GMC. My search of vendors finds the same as Mr. Alan found. The website for classicparts.com describes the spring shown in Mr. Alan's second post as fitting inside the housing that contains the shaft for the interior window crank, accessible by grinding off the rivets that hold that cover in place. Like Mr. Alan, I do not want to change that spring; I want the spring that is shown in the photo of a regulator posted by Mr. klhansen. My regulator is good; it just does not have that spring.

I made this same repair to an off topic truck earlier in 2021 for which that spring is also not available. For that case I had the broken spring, so I was able to measure it. For that case an aftermarket spring for the regulator on a 1930's Ford fit and works. For my GMC there is no spring for me to measure.

I feel certain that someone has found a spring for some application that will fit the 1947 to 1950 GM trucks. Has anyone found a substitute? Does anyone have a regulator that has that spring in place and can give us the measurements and a photo of it?

Thanks!

1950 GMC 100 Panel Truck, 1958 270,
3-spd Saginaw with BW OD,
3.73 12 Bolt Differential from a 1966 C10,
Front Disc Brakes
Bought it in pieces 9-1976, driving since 6-1978
Follow in the DITY