Shelby Cobra alternators, whether original or replica have a distinct mid-60’s appearance. Things were a little simpler in 1965 – modern technology makes it easy to get this one wrong. The original Ford alternator was known as a 1G and incorporated an external voltage regulator. The original cars came with either a 42 or 45Amp alternator. Fine for those builds, but replicas and newer technology have much higher current requirements. Headlamps, parking lights, vents, heater fans, seat heaters, cooling fans, fuel pump, it’s pretty easy to exceed 45 amps.
The 1G style can be had in a 70Amp version, but that also may be too small. With minor case modifications, the 1G is available in a Hybrid version which will output 100-140Amps – and still use the period-correct voltage regulator. Take a look at the Tuff-Stuff site, Ford alternators for various options. Add up all the amperage requirements of your electrical items to get an idea of the total amperage. It will surprise you. Driving, at night with the lights on, heater fan and seat heaters on, fuel pump running, cooling fan running – pretty easy to exceed 70 amps.
In regards to 1-wire alternators, they just aren’t period correct. They’ll work, and offer some simplicity, but we’re about originality. Some guys have ‘dummied up’ a voltage regulator on the footbox. Better than nothing, I guess.
If you plan to use a hybrid version, be aware you may have to modify the mounting as the case is about 3/4″ deeper. We’ve learned the hard way. With a little tweaking, the original pulleys and spacers can be made to work. Shelby Cobra alternators don’t require a lot to make your engine bay more period correct. And at the same time, you can make your replica drive and perform better than an original. Drives the original owners crazy – the replicas often are better.