Hi John, 1.0 - the recirculating heater isn't up to the standards of a modern fresh air heater, but it does heat the cab up well enough to be comfortable in sub freezing weather. Living in Idaho the lowest temp I experienced was about 17 below zero, but the coldest I generally drove in was closer zero - 10 degrees above. At those temperatures the heater needed to be on full defrost setting and high speed on the fan motor. 95% of the time it would keep the windshield completely clear, and when the center started to fog I just cracked the driver side vent window and that did the trick. Sounds unpleasant in those temps but wasn't bad with the cab warm (and wearing a watch cap). In temperatures closer to 30-40, medium fan and 50/50 blend between defrost/floor was enough.
In high humidity/heavy rain the heater has a harder time keeping the center completely clear, but again cracking the vent window and running the fan on high speed eliminates the fogging. Perhaps the 1960 fresh air heater I had never worked correctly, but it didn't provide any noticeable improvement in defrosting ability over the economy heater. My truck came stock with no heater, and a deluxe fresh air model was the first heater I installed. It chronically smelled like antifreeze in the cab, even though everything (core/seals/gaskets/hoses) in the system were new and there were no detectable leaks. The smell is why I got rid of the fresh air heater, and the econo heater has never had an odor problem - so lack of stink was more important to me than heater/defroster capacity, and I was driving 36 miles each way every day for 9 years.
2.0 - Correct there is no fresh air intake with the recirculating heater. If a person was creative enough with sheetmetal
I suppose you could install a fresh air valve on the face of the firewall plenum inside the cab and route this into a recirculating heater with a little fab work. If it were on the bottom of the plenum it would probably leak water when raining. This could in turn connect to a completely different heater, although I'm not sure what would be suitable.
In my search for a heater that would actually function in a northwest winter, I tried:
1. Fresh air 1960 oem unit (smelled).
2. Old Air A/C-heater system (completely ineffective).
3. An electric van auxilliary heater (useless).
4. A Vintage Air street rod heater (inadequate heat and direction control).
5. A Flexalite Mojave heater (decent heat, no direction control).
Of the last 4, the only one that did any good at all was the Mojave heater mounted on the floor between the seats. It kept my feet warm and nothing else.
The econo heater doesn't provide performance of a modern heater/defroster, but it worked well enough to drive the truck everyday in the winter, and now that it's retired to hobby duty I'm glad to have it instead of the fresh air breadbox on the firewall. Good luck with whatever you decide to do.