I didn't mount anything, it came like that. But, it does make it easier to replace the brake light switch when it does fail. I didn't have to rebleed the system when I replaced mine. I did add a few drops of fluid to the hole and I prewet the business end of the switch before I installed it though.
My E-brake cables run through two steel tubes from the cockpit, through the firewall then left and right along the firewall, then they turn down the frame towards the brakes. I can send pictures, but If your trying to duplicate what they did back in the day, it might be better to find some vintage shots.