On buses
or aircooled vanagons (I've never owned one) I understand that the
heated air sometimes wasn't by the time it got up to the front. Even
on working systems.

Mostly true. I happen to own a '75 Westy with a stock heating system in excellent condition that puts out LOTS of heat, especially in the back. My daughter has actually asked me to turn it down because it was getting too hot in the back of the van. I mention this only because there has always been speculation that the heating systems in buses NEVER worked, even when they were new.    Jeff

'74 Super Beetle Conv.
'75 Westfalia
'84 Westfalia