Well, I tried a smaller version (1,500 bpu) of the heater tootie04 referred to. It made no effect on the temperature inside the truck. I closed the partition in the sleeper to make the space smaller and sat there like an idiot for probably an hour - watching my breath turning into steam. Finally, I gave up, turned off the sucker and started the 15 liter behemoth. The cab was warm in 30 minutes
I returned the heater to the Canadian Tire and - call my crazy - bought a 10,000 BPU Kero World heater. This is very well designed and it does produce the heat I need. They don't recommend you sleep with it, so I just run it before going to bed - all the windows get covered in steam from inside
But you have to be on guard (check the flame to make sure it is blue; keep the window open to provide at least 6 sq.in. "hole" etc.etc.). The heater is very well insulated and mostly sends heat in one direction - to the front. You need at least 32 in of space ...
Of course it runs on kerosene, but I just tried it and was quite happy. 1 gal of kerosene goes for the same price as diesel, but this heater only uses 1.5-2 gal of the stuff during 10 hours of operation!
I don't know how much it goes in the U.S. for, but I paid $229 Cnd yesterday in Saskatoon, SK.