Just some info if anyone looks at this in the future as I have already communicated with Red1987Raider.

I did a bit of looking around at thermostats for the 4D56T engine ranging over 86-00 year models and there doesn't seem to be any difference in the thermostats.

I looked at three different thermostat manufacturers and they all state that it is 54mm diameter. Which is odd because Red has measure twice now and confirmed the seating area is 60mm. 6mm difference seems like a lot to me.

Still yet to be confirmed as to what thermostat is correct fitment.

Haynes manual says the thermostat is sealed with RTV also for a bit of side info.

Now post ya truck...we all want to see it <img src="/forums/images/graemlins/smile.gif" alt="" /> <img src="/forums/images/graemlins/drunk.gif" alt="" /> <img src="/forums/images/graemlins/smile.gif" alt="" />