Here is a link to a thread I posted a while back.
View topic - Forty Below Zero Deuce :: Steel Soldiers :: Military Vehicles Supersite
I elected not to go with the standard military fuel burning heater becase I feel it is complex (hard to install --- takes up a lot of room, AND I'm afraid of them.
One thing I found in cold weather is that with the truck sitting, even with the engine idled up, the engine doesn't warm up enough to allow the defrosters to knock the frost off the windshield. Until you get these trucks rolling (working) they don't build heat and in cold weather to run good let alone operate the defrosters. This is a good argument for a fuel fired heater but like I said earlier, I'm afraid of the fuel fired heater. To solve that problem I installed an electric 24 volt radiator fan and removed the 13 HP stock water pump fan.
Here is a link for the fan project:
View topic - DISCUSSION - Slobbering Multifuel Cure? :: Steel Soldiers :: Military Vehicles Supersite
I should note that after this post was published I later built a better fan mount --- see attached pics. Note --- I don't mean to hijack this thread by talking about fan stuff BUT building engine heat is part of the challenge in operating these trucks in below zero weather.
I supplement the standard deuce cab heater with an auxiliary after-market heater mounted under the pasengers seat. Because we installed a pre-lub pump and needed the engine compartment room we modified (shortened) the stock deuce cab heater and mounted it under the dash. It now serves as a defroster only unit with the aux under seat heater as a cab heater. I feel moving the heater from the engine compartment to inside the cab increased it's heating efficiency. Some pictures of the cab heaters are also attached.
I realize this is probably a lot more than you want to tackle but it gives an idea of some of the options I choose.