mein has been gone for 4 years now.  i have driven in the winter and
without the solid divider i have behind the front seats it would take a
long drive before the interior of the van warmed up to comfortable temps.

i close the bulkhead door and when it starts to get to hot up front i open
it and let some of the extra heat heat the rear interior section of the
van.  i cold days it can be a while before i bother to open the bulk head
door.

if you like to putz and really want that space you could build a system
using quick disconnects for the lines to the rear heater.

jonathan