Well, I pulled it apart and the worst part of the job is getting those damn plastic rivets out of the lower bumper cover on the LX to gain access to the radiator drain valve. Pulling the thermostat takes all of 3 minutes once you've drained a little out of the radiator and removed the bleed plug.
As I said above, I'd check my records to see how many times I've done this between my two Hemi vehicles. It's been done 5 times in 55,000 miles on the WK, including the stealer doing it just before I bought it a little over 6 years ago. Granted, two of those times were once when I changed the camshaft and once when I removed the stock 203* unit in favor of the 190* unit. The LX (the one that was now leaking) has only been opened up 3 times in almost 78000 miles, once when I first installed a 190* unit, once when putting a new one in when I changed the camshaft, and now this time.
I've also found an old factory 203* thermostat (PN 52028898AE)....most online places call this Chrysler part number a 195* unit, but 203* is stamped right on it. Anyway, I checked it's dimensions (thickness and diameter) with the aftermarket Napa unit, as well as the seal conditions and thicknesses, the thermostat housing for flatness, and the depth of the recess in the front cover. Without going into all the dimensions, I'll say that everything was close enough between the two so, by themselves, wouldn't cause any issues. The aftermarket (Napa) used seal was .005 in. thicker than the used factory one. Any irregularities in the used rubber seals were all on the thermostat housing side, not the front cover side.....which looked pristine on both seals. The front cover recess (where the seal sits) was about .035-.040 in. shallower than the used seals so the seals, in theory, should seal properly. The thermostat housing is a little rough (stamped metal) on the rubber seal mating surface and not completely flat when checked with a straight edge. So, from what I can tell, the housing is the most likely culprit. Cobra259 and nvrdone1, it looks like you guys might win the Kewpie Doll prize.
Tomorrow, or when the weather improves and warms up a bit, I'll go get another thermostat and seal, take the measurements of both, and try to find an aftermarket housing that is made a little better than the factory one. Kind of interesting stuff for such a simple setup.