My '52 has Vintage Air A/C. It comes with an ABS C-channel about 2 inches tall that attaches to the bottom of the dashboard running from about the ignition switch to the right side of the cab. Vintage Air mounts their fan, mode, heat temp, A/C temp knobs and a double set of vents in the ABS roughly under the radio speaker grill.
That leaves another 18 inches or so of empty space in the ABS C-channel before the vent on the right hand end. I mounted a red 12volt LED lamp in the ABS and used it in the "exite wire" circuit. A similar blue LED is mounted next that shows if the A/C clutch is engaged. I also mounted a blue 12volt combination switch/LED nearby that controls a bed lamp and an under-bed mounted backup light.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
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