I have no idea what it is. Possibly it could be adapted. Would be a real mess though.
The real heater has the in/out water tubes extending straight forward through the firewall into the engine bay. It is also mounted by three studs extending straight forward through the firewall. Two studs come out directly on a horizontal bracket attached to the cross air box & are accessed from inside the car, high under the dash. The bottom stud comes out inside the inner metal cross air box. There is a rubber plug on the engine side that is removed to access this stud & nut through the firewall to the cross air box. A fiendish device. Very hard to get to the attaching studs, nuts. My heater has been out twice. Once to repair a leak & once to put a new wiring harness under the dash.
Unfortunately, there is very little room in the car to fit anything else.
Don't know what to say. Check around for a correct used heater which can be rebuilt. Moss had the heater core units for a high price, over 500 USD. The whole pile of brackets, castings, clips, fan, & covers that go with it are nearly impossible to find except used.
If you are in a warm climate, it's perfectly acceptable to simply leave the heater out & plug the necessary holes. As I said earlier, cars exported to hot climates were never equipped with heaters from the factory.
D