There is a gm hydrovac for the 1 ton truck for that year
Find that one and install it in the 1/2 ton would be fairly straight forward
And find the larger 1-1/4 diameter master so that it moves more volume of fluid
That makes the brakes more difficult to press but the added help of the hydrovac will more than offset that detail
Then you could investigate shortening the brake pedal linkage to make the high point of the pedal closer to the floor for driver comfort
The shorter stroke of the pedal won’t be an issue for stopping once that hydrovac and larger master are working together in your half ton
-s
