It wouldn't be a bad idea to replace the thermostat and o-ring while you are doing the belts and tensioners. The thermostat and o-ring would cost you under twenty dollars at your local dealer. I just replaced mine on my 90. My temp. was not getting up enough and just had t-belt and belts, tensioners, idlers, plugs, wires and radiator replaced, maybe 10,000 miles ago. I looked back and noticed that I did not buy a thermostat. Now, engine gets to temp and idles like it should... Just a thought!!!
Bryan