Resistor for Temp Gauge?

[AstroMotive]

Fiddling with this '70. Had an idiot light dash originally. The guy before tried converting it to a gauge dash with the LMC number gauges. But alas he quit so now I'm trying to figger it out. The gauge pegged when we keyed it up. Sending unit is good. Correct voltage on the circuit. Still trying to figger out why the gauge pegged, but in the mean time, I was looking on here and I saw something talking about a resistor on the gauge and that some require it and some don't. How do I know which is which? The original gauge was in a box but no resistor on it... Thanks in advance for your input.