70 GTO add on Gauges

I have a 70 GTO with the stock 400 YS code engine in it. I just installed a set of add on gauges for Temp/Oil Pressure/Amps

What should be the average reading for each of these at idle then driving?- When should I be worried?

Also the Amp meter seems to peg widlly up and down- do I have that bad boy hooked up wrong or should it be moving around all the time? (looks like a tach at times) :-)

Any sage advice is appreciated

How wildly is the amp meter jumping? It'll jump up a tad when you're getting into it hard...but looking like a tach is a bad thing. Is it grounded right?