I"m not sure what kind you have but I have a 1987 F250 that came with a 70(?) amp alternator. I have added some electrical goodies and went to a 3g alternator that came off of a 1993 or 1994 Ford taurus that puts out 130 amps. Big improvement.
The only thing I did was change the position of the connections. I was told all you had to do was turn the innards but I ended up having to unsolder the insides and clock the case I forget how much. I might have been able to use it as was but the connections would have been around the 5 oclock position and I didn't want that.