Ok, here go! I have an 84Z with a late 70's 305 and on computer stuff (old school) Furthest I driven the car is about 1/4 mile (work in progress).
#1
I did a custom dash with new gauges. I let the car run for like 15-20min and the temp gauge didn't move. The after market cheepo I took out before my new ones went in didn't work ether. None of the stock gauges worked when i got the car. I'm afraid to let it run to long for fear of over heating. What could be wrong.

#2
I picked up a stock electric fan from a 87 trans am, my car now has a belt driven fan (not stock) and I want it gone. Will the T/A fan cool my car and some suggestions on wiring it?
Thank guys!

 

If you currently have a belt fan, overheating shouldn't be a concern.

A stock single fan, or one of the two single fans from a dual fan setup will (should) keep a 305 cool with the right fan switch.

The gauges are a separate issue. Also possible the engine is running to cool (no/low temp t-stat) that the gauge doesn't register temp.