Before I begin, this is a modified version of AndrewJ's and several other people's ideas...
I like the idea of eliminating the alternator, but I don't like the possible FE consequences of sensors and ecu operating at battery voltage and not alternator voltage. I also don't want to lug around heavy batteries. My solution: Alternator runs the Ecu and fuel pump only, attached to a small lawn tractor battery. Everything else runs from original battery, still in original location (just with the alternator not plugged in to it), with a (probably a relay) charge switch that connects the two battery circuits.
Here's a schematic of my plan. It allows for a cheap lawn mower battery to be used as a capacitor in the alternator - ecu circuit, and a source of power as the ecu needs to be on before the engine is turned over.
The regular car battery remains in its current state, wired to everything else on the car. I'll install a heavy gauge wire and a heavy duty "charge switch" between the two systems so I have the option of using the alternator as it's typically used. I think I'll try to use it when decelerating at offramps and down hills as well. The reason I want it to be capable of 50-60A is so if the big battery is drained down past the point where it'll turn the starter, I can use the lawn mower battery to do the job (infrequently, for sure, but a nice emergency jump-starter).
I will need to get a volt-meter to monitor my big battery's charge so I can charge it before it goes dead. For now, I'll probably wire my Digital MultiMeter (DMM) in to watch it.
I'm going to use a trickle-charger to charge the big battery nightly, and somewhere down the road I might try out some solar charging like Andrew did.
Any thoughts????