My little 302 has the same problem. It runs too cool. Needle never leaves 60 for most of my driving. If I romp around in the mountains in third gear i'll get it to about 85. Only on the track, which God bless America, will be this October the 11th, does it get to 90C. So, I bought a Canton
oil thermostat and just haven't put it in. It requires wrenches and all that greasy stuff and so I just haven't done it.