Yakimabowtie,
My truck was in pieces when I bought it. I don't remember much about the configuration of where the clutch arm and brake attached to the 3 1/2 " shaft. I do know this, if I just put the brake arm on the shaft then one of those "C" locking clips would secure it nicely. It's as if the 3 1/2" shaft only accommodates a brake and the truck did not have a clutch arm attached. The problem is with only the brake arm installed the pedal going through the floor would have to be redrilled to the right. Also, with the new power brake booster I'm installing the part that pushes the plunger needs to be about 7 1/4" off of the frame. Here is the thing I'm thinking - did Chev make a shaft 3 1/2" long for trucks that had auto trans which would explain why only the brake pedal fits correctly (clutch arm wouldn't be needed), and maybe they made another shaft about 4 1/2" long when there was a clutch arm attached as well as a brake arm? As I said before, the clutch arm is 1 3/16" wide and the brake arm is 3" wide. With the clutch and brake arm on the shaft it equals 4 3/16" but the shaft I have is only 3 1/2".
