This is one link on a drilled thermostat. Doing a search will provide more if you need it.
In this picture
Both of them labeled as #3 are for the tensioners. One for the supercharger belt, the other for the accessories belt. Both are reverse threaded, as you turn the bolt counter-clockwise to remove the tension on the belt. If they were standard thread, you'd loosen the bolt before the belt. The #3 next to the #8 is the one that you're working on.
Black 2000 SSEi, Silverstar Headlights, Angel Eyes fogs, 3rd brake light overlay, hi-flo cat, drilled 180 degree thermostat, Intense FWI, PCM, shift kit, and 3.4 Pulley. Solid front mount.