Anybody use a 73 up duster heater box ina 71 duster?

I'm not sure about a heater only interchange, I am currently modifying a '70 duster to accept a heater/AC box from a '74 Scamp. It appears the flat mounting surface where the old heater box mounts will cover the new stud locations, but they will have to be re-drilled. The fan hole is offset and much smaller. The evaporator core connections are offset toward the pass. side and a new opening will have to be made for the heater hoses. Other than that it looks like it will work out fine.