I have a 1975 F-250 High Boy with factory air, 360, and C-6. I accessed the heater coil by removing the air conditioning coil from inside the cab. Once the A/C coil was removed the heater coil is staring right at you and comes straight out. Before removing the A/C coil, I removed the blower; but, could not access the heater coil. Not possible on my truck.