The position of the T-stat housing doesn't help much trying to get it to seat properly.

Ford Engineer #1 "Hey, you know, changing the thermostat on a Chevy is WAY too easy, lets put ours standing up instead of laying flat"

Ford Engineer #2 "yeah, that would work, but WAIT! Lets also put it BEHIND the timing cover, and so close that you can't use studs, that way, it will take FOREVER to change!"