1. At the time, the best price on Amazon was a 2 pack for $6, so I already had the extra unit.
2. The thread and wiring diagrams I could find weren't clear to me if both circuits could run through the same rectifier.
3. I figured the best place to house the rectifiers, and interrupt the wiring harness was at the toolbox. I pulled the original taillight wiring back, drilled two holes from under the fender all the way through the toolbox, fed the original harness through one hole, and the new LED taillight wiring harness through the other. I zip-tied and velcro-ed the rectifiers to the top of the toolbox where they'd be secure and very well protected. Doing it this way also allowed me to not cut the original wiring harness in case it didn't work out or I wanted to revert.