Well, I asked for opinions and I got them  - overwhelmingly it is keep the rear heater!  

I like the idea of ditching it for a Propex or similar, but that is just too much money right now, 
and due to heay salt use in the Northeast, the van is off the road for the winter anyway - and I 
have a weekender interior so I don't have  propane tank - not that I couldn't add one...

So now I will replace the valve, core, O-Ring, heater hoses and I might even splurge for the 
plastic T's.  It's nice to rehab a complete system. 

Thanks again
John
87 VW WWW or VW^4
(VW Wolfsburg Westfalia Weekender)