For clarity the MG fan I used needs to run backwards (simply reverse polarity) and I used the MG fan cage also. The cage spins backwards but I felt it moved sufficient air. But, do note I live in So. Cal. and heating requirements are lower here than other places. As is obvious this was necessary for a Turbo 2.3 swap, but I see you are doing a V-8 swap. I agree with Jerry (Old Kayaker) there are many options with heater motors. Mounting the motor is relatively simple as they typically only have 2 or 3 screws.
I stumbled upon the MG fan only because we used them as replacement motors in our Sunbeam Tigers. I had done the swap, but never put the housing back in the car. Then when it became obvious the Pinto needed clearance ... the rest is history.