jiM - I highly recommend installing a thermostat. Otherwise the engine's gonna be running cold all the time. This results in rapid build up of condensation inside the engine, dilutes the oil and shortens engine life. Also a cold engine will burn more gas and just generally doesn't run as good.
If you have an AutoZone nearby, suggest their #800-180 (about $4). Otherwise get one from your IHC dealer - figure on $15 - $20 however.