[dwtaylorpdx]

So the premise is that if you drive the alternator from the axle instead of on the engine and if you put a switching circuit on the accelerator pedal to control when the alt charge to only happen off throttle, you might save energy. Maybe add a circuit to the brake lights to trigger full charge when braking to maximize the use of the parasitic nature of the alternator.

You can buy rear drive axle mounts from Jegs and Summit as well as other stock car sources. They use the pinion seal bolts and a strut to the rear cover bolts to mount them. Easily built as well.

A pulley could be sandwiched behind the CV on a FWD car, and a simple steel mount from the transmission bolts and any other convenient spot. A mitsubishi forklift alternator strikes me as the best option, they are tiny, relatively inexpensive and light weight and produce about 45 amps.
If you were really lucky you could install a fwd alternator backwards and it might be close enough to use some spacers to line it up with the drive axle cv at the transmission end...

This method works especially well on a race car where the engine is revving beyond what alternators really like to turn. (Like 7500+) But the speed increase it allows down a straightaway is measurable. Which implies a savings in power lost to the alternator thats pretty impressive.

Dave