Zildjian was right

. I am seriously considering a Chinese diesel warm air heater. Which output have you chosen? I have seen 2Kw, 5Kw, and 8Kw.
On the heater forum threads, some people have complained 5Kw is too much for a small van but I can't see it myself as they are thermostatically controlled. Bigger is always better in my book. With a dedicated fuel tank you have the option to go RED I suppose, but I have read where people have tapped the truck fuel tank to save fiddling about filling the small tank inside the cabin.
Might I suggest you think carefully about where to put the heater? There seems to be a problem getting heatproof ducting at an economical price as I have seen some with 4 outlets.
My own plan is to site it near to the toilet/shower room to be able to use it as a drying room (Zildjian again

)
I hope you supply plenty of instructions and photo's
Best of Luck with it,
Mark
"Success consists of going from failure to failure without loss of enthusiasm" .......(Winston Churchill)
2007 Ford Ranger "Thunder" 4x4
Camper aedificavit domum
2016 Ford Ranger "Wildtrack" 4x4