A one wire alternator does not use the factory charging system wiring...OnE wire...direct to the battery or starter relay battery terminal....does not go into the bulkhead wiring..
It only hooks direct to the battery if YOU wire it that way. Some may very well hook it to the original charging wire.
I just don't like "one wire" alternators and no real reason to use them. You DO want to hook it direct to the battery with OVERsized wire if you want decent voltage sense
Also keep in mine that with a trunk mount battery you need to figure out a way to kill the ignition line to meet NHRA, IE use a 4 terminal, SPDT switch (It's not a "4 pole" switch)
