The only way you can do what you are describing is with a one wire style alternator. You will have to have an exciter wire and a voltage sensing wire if you want to use an internally regulated alternator. Some of the later style alternators use an internal sensing regulator that reads the voltage sensing off of the large output wire terminal which is connected to the battery/ main terminal circuit. I believe 94 and later years have this feature.
Otherwise the exciter wire (usually the brown one) will be connected to the "L" terminal and the sensor wire usually Red, will be connected to the "S" terminal on the alternator. You should notice the terminals on the alternator will be labeled "P L I S" or "F S L P". The brown wire can be sourced from any key on power source but you must install an inline resistor recommended 85 ohm 5 watt to 300 ohm .5 watt to protect the alternator internal diodes and prevent feedback to the ignition circuit when the key is shut off.
Here is a simple wiring diagram I developed to illustrate this wiring to convert the stock OEM trucks to a newer CS alternator.
There will be other helpful answers so pay attention to them as well.