temp gauge is reading 150f+ when cold??

i have an 89 xj 4.0 and recently saw my temp gauge start (when cold)from 150f+ and when normal running temps are reached will be right on the red.
i just flushed the cooling system and replaced the thermostat with a 192
and was woundering if it was the temp sending unit or gauge(s).
my fuel level also reads off but i believe that is due to a dying fuel pump/float.
all and any help/ideas are appreciated.
thank you.
crash02

Sounds like gauge ground's clean all ground connections, on the dipstick bolt, the back of the engine to firewall, driverside fender and battery.