arveetek
Adventurer
Lastly I want to figure out how to wire the stock Blazer tail/brake lights so I can plug them into the 4 pin of the RV so I can ditch the magnetic trailer lights.
I recommend these diodes from Roadmaster:

HY-POWER DIODES
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Essentially, you cut the factory wiring going to the taillight, then splice one diode in on each side. You will have two inputs and one output: one input is the factory wiring and the other input is from the 4-way from the motorhome. The output goes to the taillight. Makes it a cinch and keeps everything working properly so there's no backfeeding through the turn signal switch. Simply run a dedicated, permanent flat 4 wire from the front of the Blazer to the rear, and then use a short quick-disconnect cable between the front of the Blazer and the rear of the motorhome.
You don't need a diode on the clearance/running circuit, as it can power up all the clearance/running lights on the Blazer with no problem.
Casey