When you replace the temp guage, replace the fuel guage at the same time.
Other things to keep your CJ cool:
Make sure you have the fan shroud installed (this is essential!!!)
go with a 180 degree thermostat
flush the cooling system
Inspect the fins on the radiator and make sure
that there's not a large chunk of them folded over. If they are, you can get a radiator comb to straighten them out.
Make sure the cooling system flows through the intake manifold and that it hasn't been bypassed.
Make sure the heater core hasn't been bypassed.
Make sure you don't have a clogged hose (due to corosion)
I had to do all of these things to get my CJ running cool, but now I can creep along all day in 100 degree temperatures without it overheating.
Ricers make great Jack stands! Give 'em a try!