Low engine temps

maybe the fan is locking solid. does it get hotter at idle? (i am at a loss & just throwin stuff out there off the top of my head). Late M-body radiators are very efficient, you've got a 7-blade viscous fan, an AC style waterpump AND a shroud. All this stuff is very efficient at transfering heat. On a relatively mild 318 and heads that are noted to not need much timing [fast burn], all this equals a cool running engine (yes, that are known for running cool) {remind me to copy your exact set up when I set up my A body with the stroker motor and roller cam.} One thing that you must remember is that even if you replace a suspect part with a new one, it does not mean that the new one is good either. Especially with something like a thermostat (the quality seems to be going down on these things). You may need to try the old "putting the thermostat in a pot of water on the stove with thermometer trick" to check and see where the thing is actually opening. (sorry for long post)