I used a Stant Superstant without problems.

Be sure you get a 190F-195F thermostat as this is the correct one for a V6, and anything cooler probably won't even cause the temp gage to go upscale.

The temp gages in GM-V6-Powered Troops typically read low anyway, normal range is usually around 1/4 to 1/3, if it's up around halfway you know things are getting toasty!

'90 Troop 3.4 LS
'89 Troop RS (Has Valve Issues, needs Counseling)
HI, I'm Ed and I'm a Trooper-holic!
Keep On Troopin'......