I wouldn't go out of my way to buy an LSx alternator. The Units used on the GenIII are a big bulky thing that's overkill for a Cobra. I think they deliver 140Amps or something like that. Considering our cars have no A/C electric windows etc you dont need the big alternator unless you are going to fill the thing with speakers and amplifiers.
I bought an 80Amp Delco unit from the wreckers for $55 and then built my own brackets. Its a lot more compact giving more options for mounting it.
Only 3 wires needed.
1. The main output wire, you can run this one round to the main cable on your starter if you have the battery in the boot.
2. Exciter lead, this one should be hooked to ignition battery so that the alternator is energized when you have the engine running.
3. Charge indicator, this one should be hooked up to a bulb on your dash with ignition battery on the other side of it. As the alternator output voltage ramps up it will reach the same potential as ignition battery and the bulb will go out. If its over charging the voltage will be higher than the battery voltage and the bulb will light. If it's under charging the battery potential will be higher and the bulb will light. I still like to have a volt guage on the dash as well.
Cheers