Heat Shield holes in 4x4 cab???

[HOTFUN]

Well I need to back track on what that top hole is just to the right of the speedo hole. I looked at 8 different cabs on my place today and there is no rhyme or reason to what was in that top hole if it was drilled. Two trucks had a factory camper harness that a 10 guage red wire came out of that grommet. Another big block had what appeared to be two wires probably emmision relay related. Another 350 cab had nothing, and two had the emmisions full harness coming out and going to the gutter across the engine compartment. But two trucks also had factory installed tachs and one came out second hole and the other the third hole as the brake booster brace about covers the second dimple down. Just some observations. But those two holes in the lower firewall are definitely the big block only heat shield mounts.