64-66 Recirculating Heater

[da_bears_da1]

I am going for a clean firewall look and have bought a recirculating heater to replace my Thrifty Heater. I looked in the shop and assembly manuals and did not find any installation instructions or pictures.

I would appreciate instructions, pictures or directions on how to mount the recirculating heater to the firewall. I know I have to drill another hole in the firewall to accommodate the core. Do I just drill a hole above the existing hole and then just line up and drill holes for the mounting studs? Any help would be greatly appreciated!