I had a 2006 TJ. Its been a number of years, but as I recall my TJ had an extra battery tray near the steering column. I didn't have an extra battery so my extra battery tray was empty. There was a bolt in the rear of the tray that wasn't too far from the firewall where I had run the ready brake cable to the break pedal arm. I used an L bracket bolted to this bolt on the extra battery tray. I bent the L bracket slightly and bolted the emergency break away box to the L bracket and was able to run the break away cable through the firewall to the brake pedal arm. Hope this helps.
2018 Thor Tuscany 42GX
2015 Jeep Wrangler JK Unlimited