master cylinder pushrod interchange

Or this adjustable pushrod from Doctor Diff

http://tinyurl.com/msyyh6

I am using it with AndyF's late model adapter, and an 82 Dodge truck aluminum master cylinder and it works fine, but I think I could have stayed with the original single pot pushrod and adjusted the brake light switch.

I have a question though, about the brake pedal, mine isn't fully returning to the "up" position, I have to manually lift it a little with my foot, or else it puts a drag on the front calipers. For stock vehicles, usually there is a spring/rubber boot thingy that goes around the pushrod to help return the cylinder to the top of the bore, but I can't use it with this pushrod. What is the usual thing that keeps the pedal in the up position? My car is a '64 Valiant, and there is no return spring on the pedal...I was thinking of adding a simple spring to remedy this...