My L 110

Sounds like I will need to borrow a computer once I get some progress pictures saved up.

I kinda figured the heater must have another source for fresh air but I wasn't sure. As for heater condition I will be recoring it for sure and reconditioning the rest of it as needed. The cooling system will be all new as well. I will be replacing the floor pans and carpeting the cab floor and back so it should hold the heat.

We have been very lucky to have thawing temps during the day right now so I have been busy in my shop, I don't waste good weather ever!

As far as I know there is no other source for fresh air to the heater. The cab is not tight enough to prevent fresh air from entering at will. The heater fan just recirculates the cab inside air that mixes with the air seeping in through the cracks. If you've ever driven one of these trucks down a dusty road with all the windows rolled up, you'll wonder where all the dust got in the cab. Through the cracks everywhere.

I bought a fresh air heater from a R160 gravel truck. There was an adapter with a door that replaced the deflector over the square firewall opening. the heater was totally different than the original dust collector and really made some heat and even the defrost worked. Imagine that. I do not have pictures any more. I am thinking that this fresh air heater may be more common in the larger trucks with the COMFO-VISION CAB. These heaters are out there, now to find one, more.
Our resident know-it-all parts person would have more experience with this than I.

FWIW- The Heater core in my '55 is all brass. Imagine my surprise when I pressure tested it and found it to be leak free- Perhaps yours is too. My truck has air leaks (major blowing wind) all over it and the heater still managed to make me uncomfortably warm at around 40*F. Granted that's fairly warm, but maybe it'll give you somewhere to start from.

Well thanks for all the information, it is very helpful. I don't think a recirculating system would be very effective at defrosting the windows. As well I imagine I will be fixing a number of the leaks and installing better door seals. I 'm in Alberta and -40 is not unheard of, I probably wouldn't drive this truck in that kind of extremes but I want to make sure the heater will get the job done if needed. I will have to see if I can modify it to pull fresh air and I might add louvers to the cowl vent.

I will have to take a closer look at my parts truck as someone has retrofitted a Ford heater in it and perhaps it is a better setup. If all else fails I will fit it with a late 80's Mustang heater box, but the original in my truck is much more compact so I rather make it work if I can.

As for pressure testing, I may consider that, sure they put pretty heavy cores in them. I just don't think I want to risk it, could be messy if it burst later and I hate redoing stuff.

Pressure testing should be in the same range as your radiator, Low pressure, around 7 to 10psi should be adequate. Look your heater core over good, you would probably notice any leaking areas by discoloration.
My thoughts only

Since vehicle cabs - cars included - today don't have the vent windows in the doors, that is the source, I suppose, for the fresh air make-up of that era. Just crack open the vent window enough to allow additional air to assist with the defrosting. Remember, life was a little slower back then and people were willing to tolerate slowness. You slowed down when your windows fogged up, not speed up the fan. Most fans only had on & off. You slowed down when the rain was coming down faster than the vacuum wipers could keep pushed off. And on and on. You were able to adjust to the conditions as drivers are supposed to today, but so often it's "full speed ahead" now. A/C systems keep widows fog free, we have multiple speed wipers, etc.......... We have forgotten, or are too young to know, about the ways of the past.

My only complaint thus far with respect to the factory heater on my truck is low CFM. I think it has to do with the squirrel cage being buried in the bottom of the heater housing. I can only assume the standard fan attached to the top of the squirrel cage is designed to "feed" the lower fan element. I am planning on adding 2 dash vents and possibly a floor vent for the drivers side. I am concerned that the current housing simply will not deliver enough CFM to satisfy me. I would construct a change over valve so that I'm not running all of the vents at one time ( dash or defrost and/or floor). This may be an instance where I would be happier starting with a modern unit and engineer it to fit my application. I too would like to pump fresh outside air through my vents, and possibly have A/C down the road. I'm not yet convinced that A/C will be needed here in MN- time will tell.

Interesting, my heater is totally different, it is long and slender, it also has the modern style fan on it. Perhapes the Canadian trucks used a different heater? As well both my L & my R parts truck have defrost vents. Do some trucks not have any? The heater in the picture looks like the Ford one in my parts truck.

I will take a closer look at my heater and see if it is the original for sure, perhaps someone already did an upgrade.

One more thing I would appreciate input on; many of you have done frame swaps, how do you deal with registering it? Do I just ignore the Dodge vin on the frame and give them the IHC vin? Do I give both vins? Clearly it would be illegal to remove the Dodge vin from the frame and or add the section of frame with the vin from my L's frame, right?

I know all this varies from place to place and laws change etc. I'm just looking for the best approach. I do know people in the biz and heard many stories but there seems to be a lot of grey area 's when it comes to vehicle modifications.