1970 C/10 Brake Booster Bracket Question

[cericd]

I have a 1970 C/10 that originally came with manual drum brakes front and back. I am adding a front disc brakes and a factory Delco/Moraine brake booster, new master cylinder and disc/drum prop valve. When I was getting parts together for this upgrade I purchase a set of brake booster brackets from someone here on the forum and there were two booster support brackets included. I can't figure out where they bolt up to the firewall. I'm thinking that these support brackets may have come along in 1971 with the addition of factory disc brakes.

Did pre-1971 trucks with drum brake boosters not have these brackets?

Are they necessary now that I have a booster and front disc brakes?

Here's a picture of the support brackets I'm referring to.