Duster firewall?

I’ve been scratching my head for a couple weeks now on this problem I’ve been having. I bought this car off of a guy as a roller, supposed to be a 73 duster. I have done quite a bit of work on it and I’m stuck on getting the heater box in it. I bought a nice used heater box and tried to install it and I never could get it to fit properly. So I got on the internet and started looking at duster firewalls and the hole where the heater motor comes out, none of the firewalls I have seen look like mine and I can’t get this heater box and motor to match up to the holes. I have included a picture of the firewall in my duster and the hole where the blower motor is supposed to come out. Anyone seen this or know what’s going on?

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