This thread will help you convert to the internal regulated alternator.
The internal regulated alternator uses a solid state regulator which gives a more stable voltage output with greater reliability, more voltage at idle, no dimming of headlights and more current output.
http://67-72chevytrucks.com/vboard/s...d.php?t=417872
The higher voltage output means more current in the circuit with the same resistance.
This equates to less resistance in the same circuit than before, which translates to a possibility of a higher temperature reading. I would doubt that it is the main cause of the temp gauge reading higher, but who knows. The temperature gauge reads hotter with lower resistance from the sender, however the engine temperature will decrease the sender's resistance to ground, and also increase the reading.
I think most of these small blocks should run a 180 degree thermostat. JMO