Installation of a Vintage Air A/C system enabled flattening out the metal surrounding the factory heater box area. This required substantially enlarging the factory hole before plugging it up with a plate. While the factory hole is relatively small, it is surrounded by several contours. Precision Coachworks' Shane Wagner trimmed the area around the factory hole with snips and a die grinder until reaching the flat portions of the firewall. At this point, the body was placed on a custom jig, but this procedure can be performed just as easily on jackstands.