I picked up my diesel webasto cabin heater used for $400. Did not come with the fancy timers, but worked great since it is instant heat. Very little battery draw as it only needed it for the glowplug and small blower fan. Easy to pipe into the fuel line. The only issue is where to put it. Like I said earlier, I had an '83 110 RHD, so under the drivers seat was the tool box area, which fit the webasto perfectly. The output was about a 1 1/2" diam tub which i mounted to the lower floor bulkhead behind the driver seat. It also had an air diverter to postion the flow from there.
Check the used market, and of course buyer beware when buying used.
'97 D90 NAS
'06 Argo Avenger