Voltage meter bouncing continuously while running

SOURCE: my 1986 ford ranger 2wd runs great, except when i come to a stop

if it is not idleing right the volt meter will go up and down is it fuel injected or carb?

SOURCE: When accelerating alternator light comes on.

Possible loose or worn alternator belt. Check the condition of the belt. If it's worn, replace it. If it's just loose, tighten it up.

SOURCE: tachometer bounces and idiot lights come on

well that would lead me to believe that your crank position sensor is going bad, and it will not show up on a computer scan for fault codes, I would have it checked along with cam sensor and replaced if necessary, before you get left somewhere desolate and the car wont start even after the sensor cools down

SOURCE: charging gauge bouncing back and forth starts after jump

Change the alternator and regulator.
Make sure all are grounded well and connection to starter solenoid from alt output is clean and tight.
Have battery checked.
Old batteries fry alternators.

SOURCE: 2005 Ford Taurus 24V DOHC.

It is your ECM. The ECM controls everything that you are talking about. If it was just not starting right away, I would say that it was the fuel pressure regulator. And still could be. The fuel pressure regulator has a check valve in it. When the vehicle sits for a long time the fuel pressure regulator could be bleeding off pressure. That is why it would start faster if you let the fuel pump run for a short time before starting. But if the ECM is bad then that would cause the gauges to go crazy. And the ECM is what tells the fuel pump that there is enough pressure. So I would suggest a fuel pressure regulator first. Since it is a lot cheaper. But it is one of those two.