Wow! very lucky... does it work? Cant say I really know what the CF designation was for the 1/4T that preceeded the Iltis - and that we used, but suffice to say, by comparison, it was a POS and not one single 1/4t vehicle (prior to the Iltis) that I had the misfortune to sit/ride/drive in - in February - had a heater! OTOH the 3/4t was a very sophisticated vehicle by comparison.
There were three different models of 1/4 ton that preceded the Iltis, and all had heaters. Working backwards, some of the reserves had the CJ7 (modified civilian vehicle, so it had a decent heater), then there was the M151A2, and the M38A1CDN3 and the M38A1 CDN2. However, since I note that you mentioned the 3/4 ton M37 Dodge, you may be dating yourself slightly and also have had the pleasure of using either the original M38CDN, or the M38A1CDN. Both of those were of early 50s vintage, and heaters were not installed in all of them. The early 50s models stuck around until the mid 70s.
Now as to how effective those heaters were, with button type canvas tops in the arctic temperatures of Manitoba, varied. The M38A1s fitted with coolant type heaters could be counted on to defrost the front windshield and heat the co-drivers feet. The M151A2 could be counted on to defrost the windshield....it had a smaller 15,000 BTU heater, where the M38A1s had a 30,000 BTU heater. The real winner was an earlier Jeep with the South Wind gas heater. Now those could be set up to crank out the heat.
The heater in the Iltis was much better than the SMP vehicles that it replaced. That is just about the only concession I will make to the Iltis. I will admit to having replaced the heater doors and the little strap that retained them over and over again until I took an Iltis out on a road test on a cold day. Half way around the ring road in MooseJaw, I too ripped the little doors off.
A few years later, once posted to Shilo, I found myself installing an Iltis heater into the cab of the MLVW. There was something about the design of that heater core that actually let the heat transfer. There was so much heat off it I had to install a thermostat on the dash of the MLVW in order to keep the heat below 75C, even on the coldest of January days. I left the original heater installed in the MLVW just to simply defrost the windshield.
Over the years I have owned many of the vehicle types I mentioned above. M38s, M38A1s, an M151A2 (actually bought 30 from the army for $110 each but had to turn in the bodies for destruction after stripping whatever parts I wanted), M37s, and a couple of MLVWs. The collection of military vehicles grows and contracts, then grow some more. But I will assure you, there will never, ever, ever, be an Iltis in the collection. Nor an LSVW.