I have thought about the passenger's side location quite a bid. It never seemed that big of deal to move the fuse block over and install it in the center to give the driver better heat. I now think the main reason is the water lines on all these heater came straight out the back. Which would put it right into the back of the engine. That makes sense to me now. You would have to solder elbows on to the back of the heater.Even if you did that it would still be a pain to get to the nuts to hold the heater to the firewall.
Probably install my Nippon Denso in a early FJ40. But I will go to the extra work to put it in the center. Unlike the dealership my labor is cheap.

John
Probably install my Nippon Denso in a early FJ40. But I will go to the extra work to put it in the center. Unlike the dealership my labor is cheap.

John