I put one of these in my truck for camping/road trips. I haven't used mine much, I was going to wait for the camp out to talk about it, but I wanted to mention them sooner in case the supply gets tight
here's the one I got, it has a metal housing. there's some complaints about the plastic housings flexing and causing the fan to rub.
https://www.ebay.com/itm/de-5000W-Air-Diesel-Heater-5KW-12V-Silencer-for-Trucks-Motor-homes-Bus-ee/372535058461?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649these are not new, a couple german companies have been making them for decades, mostly for sail boats but they cost about 1,000$. china started cloning them a few yrs ago and the prices really came down.
most reviews are good, most issues are from poor installations
I have a diesel p/u so it's perfect fit for me. they take 8 or 9 amps to fire up but only use 1 or 2 once running. they burn between .5 and 2 gallons a day aprox depending on the setting
there's a lot of info on youtube, but most videos are shade tree guys like those 2 vids.
this guy seems to know them very well and has a full series if you want to know more
https://www.youtube.com/user/johnmck1147/videossome kits are complete, some are not, so pay attention. different kits come with different thermostats. I have the simple dial t-stat.
avoid the 8kw, it's just an over priced 5kw
guys are running them in van and cargo trailer conversions, old rv's that need a new heater and even work shops or garages
there's a portable version with everything installed in a small box, just needs 12v