I was not happy with the way the heater was fastened to the firewall. It required two people to R&R the heater, and that's not acceptable. So, I took apart the heater and installed four Allen Head 8 x 32 x 1.25 inch screws (with lock washers) from the inside of the heater case. This allows setting the heater in place on the inside, then from the firewall side pulling the heater tight with nuts and lock washers.
Allen Head screws protruding as mounting posts
1/8 inch spacers held in place with high temp silicone
