Originally Posted by idroba
Probably not. Although the box size may be the same, the new ones have a different electrical connection system, different cooling vent holes for the electronic ignition, and usually a different gas inlet location from the one you have in a '72. The outside inlet and exhaust tubes probably are in the correct location.
I would recommend you consider changing both the guts and the box both. It is not difficult to remove the box, it is generally held in with only two screws in the bottom, near the front. It will slip right out, assuming that you are not one of the unlucky ones with a furnace with a shelf on top of it, and a bar in front of it.
Let us know how you make out.
Apologize for dropping off the radar about the furnace. Haven't tackled it yet - summertime. I did install a new Olympian catalytic heater and it worked well for the 'cool' winter nights here in the south. I do want to revisit the furnace eventually, just too many other higher priorities right now. One thing I have learned is to take the challenges at a moderate pace, one at a time. Otherwise, it turns into work.