Low coolant Temp

[ZeroNthedark]

I think my truck has same type of issue. '05 379 w/ 475hp 870 won't get warm this time of year. If it sits still for awhile the temp will be up to 180, but driving, while outside temp is 50 or lower, it won't get above maybe 125 on gauge. Drove a Sterling(w/ Mercedes motor) that did exact same thing, so kind of used to it, but makes winter driving a bit annoying. In the summer temps are fine, regularly around 200, but once it cools off forget about heat.

Should I look into a thermostat? And if I remember correctly, I have a 2-piece assembly, so what do I need to look out for?