Bill,
Starting in, I think 1956, 2 ton chevys had 6 lug stud piloted Budd wheels. I don't know how long that lasted, or what came next.
I really don't know so much about trucks after about 54 or 55.
But I am sure true stud piloted Budd wheels were used on some GM trucks. you are right though, the majority of medium sized GM trucks have hub piloted wheels.
Grigg
