Like many users here, my old alternator is not cutting it. My stock charging system has dim headlights at idle and dips far into discharge when ac is switched on. When choosing a new alternator, is it possible to go too much amperage? Looking through the Moparts archives, I know that high output alternators should be wired direct to the battery with a fusible link (8gauge wire/10gauge link) and this bypasses the stock amp meter in the car. What else should I look at? What is the difference in single wire/3 wire alternators?

your alt will only put out as much as the car pulls, not more than that.

that being said, there are times where your car could pull max amps.

different alt types.
single field, pre 70's alts have a single field and 1 charging line.
dual field post 70 have 3 wires, 1 charging and 2 field lines.
You can use it with a single field voltage reg by grounding one of the 2 fields.

single wire alt basically have an internal regulator instead of the external typical mopars have.

I currently run a 5.9 mag motor using the single field voltage reg with 1 field grounded. 120 amp alt.
there are some modern 100 plus amp alts that will work but you need like AndyF's mounting brackets.

They make 100 amp conversions for the square backs as well.

typical parts store alt square backs are 74 or 78 amps if you look for the 89 new yorker for your car choice.

Most single wire alt I see many run are just that. The only wire you have is the 12 volt output wire as they have an internal regulator and they self excite the rotor as soon as it starts turning. Ron

Okay, that makes sense. Mine is a 1973 with 3 wire alternator. I think the last time I bought an alternator it may have been a sad little 60 amp.

383 man, does that mean alternators with field wires may excite sooner? Possibly at lower rpm?

Not that I know of. The have enough magnatism in the rotor and stator that they self excite once they start turning but I am not sure how fast it has to turn to start charging. I would think idle speed is enough as I have not heard anyone complain about them not charging right after starting. Many racers like the one wire alt as its less wires and cleaner looking. But once the excite themselfs they just get stronger right away and start charging good. Course then the internal regulator takes control of output. Ron

there are 2 sizes of alt pulleys, make sure you have the smaller one (I forget the dimentions right now). You might see what dia crank pulley you have tho subbing one in is a pain cuz you need the right offset unless you have a good stash but I would see what you currently have