[patrickt]

Normally, it's a pretty easy job to switch out a thermostat and not have a puddle on the floor when you start her up... but you know that. I would guess that either that chrome thermostat housing or the flange that it mounts to is warped. Pick up a new housing off of Ebay, even if you don't like the way it looks, and see if you can get it to hold with a new housing. If that leaks just as bad, then I would guess the flange that it mates to is warped or cracked.