After doing some inventory on Firewall Forward kit (separate entry), obtained the cabin heater box and associated control connections and used to fit to firewall as per instructions. Used 2" hole saw (called for 2 1/16" which is difficult to find locally) and deburred edges with die grinder. This made the outlet pipe to fit through the hole in the firewall easily. Drilled mounting holes for horizontal orientation and then drilled mount holes for control bracket. Of note, had to drill out the arm on the heat box to accept the cable swivel stop & screw.