I'd use the donor harness every time, but I've been doing (and teaching) automotive electrical work for over 50 years. It's there, it's free, and I'm not too stupid to understand color codes and follow a wiring diagram. Your mileage may vary!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!