First thing I'd check is that the connections on the back of the ammeter are tight - review this article at Panteraplace:
http://www.panteraplace.com/page178.htm
Next, check that your battery is still fully charged, if the ammeter is acting up, then it may not have been passing enough current to the battery, and it's discharging.
As for the tach, what do you mean by 'Crazy'? When my voltage regulator blew, I found that when I revved the engine, too much voltage was being passed through (18+ volts), and my tach. would rise to around 3000, then drop to zero until I shifted, then do the same thing in each gear. If it's anything like this that you're experiencing, test the voltage going to your battery - a simple volt meter that plugs into the cigarette lighter socket will do the trick ...
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