Stazi's right.

When I replaced mine in my last CSVT, I got the 160 degree thermostat and the Dealership sold me a "non returnable" gasket with it... which under further observation, wasn't required. You can use the O-ring from the original Thermostat (if there's no crack, swells, etc), or order one from Ford ($1.22.. not sure of the part number, though)

2006 Pontiac G6 3900SFI GTP Coupe CAI, Stainless Cat Back, Vector Tune, Strut Brace, Eibach Pro Kit, Custom Made Projector Headlights, 4300K, 20% Tint Former Owner- 2000 "Stryped" CSVT CEG Dragon Run- Oct 13-15