I've read on other forums that those chinese "Chinebasto"
heaters work very well.
You may think to buy a 5 Kw unit, more heat produced than the 2 Kw unit (seems obvious, hehe).
One point of attention is the incline angle you have to put on the fuel pump, for about 30%, the suction part of the pump needs to be lower than the pressure part.
I have a second hand bought german Webasto in my truck, I installed first the fuel pump above the suction level of the dedicated tank I've put for the heater, and I think the pump constantly sucked air somewhere.
It's problem I didn't cure for the moment as I went the LPG heater route instead, but what I will do very shortly is to re-route the fuel pump under the fuel level, with a cock just at the tank's fuel outcome.
Oh, by the way, they are noisy when working, and be sure you have a battery at the top level, and finally, be sure you order the right voltage, 12 or 24 V, depending the usual voltage of your truck
Here a picture of the Webasto fuel tank.