I had a slow leaky rear heater core/valve. I plugged the hoses with bolts and teflon tape as a temporary fix.
Somebody (sorry I can't remember who right now) told me that a VW Rabbit heater core will fit with a slight modification to the rear heater box, and is much better built that the Vanagon rear heater core. Sorry for the short and sweet here, but I am running late.

See ya,

T Root