can the rear heater be simply disabled.

Easiest way is to just hook the hoses that go to the rear unit together as close to the engine as possible. May need a special connector (hoses prob. diff. size) and 2 clamps, avail. @ NAPA i am sure! Other parts stores should have it as well. If need be, cut a piece off of each hose to take to parts man for sizing. Get a metal connector if aval. at your store!!! Plastic will work but have seen some collaspe.