Rod–The Corvair station wagon and the van version had an additional problem.
Because the engine was–literally–inside the passenger cabin, and because the heater boxes tended to rot out after a few years, exhaust fumes would seep into the cabin, with sometimes disasterous results. I vividly recall the case of a carpenter who used one of the Corvair vans for work, and he was turned into a brain-damaged vegetable by long-term CO exposure.
Also–the maximum payload of the pickup and the van was greatly reduced by the weight of the rear engine. Having a rear engine in a vehicle designed to carry large loads in the rear is…not a great concept.
All-in-all, not a good design.