[LH Lead-Foot]

The diodes are a nice touch, but in most case are not required as the relay open the circuit. They do help on vehicles were serial data communication is used every where are when the fans are shut off, they act as a generator producing voltage back into the system as they wind down. HVAC blower fans have caused several tech bulletins over the years, but what you have is good to go. Aftermarket A/C clutch can induce 180 volts when de-energized and cause all kinds of hell other than popping in the radio speakers.

I do like using factory type parts for the job at hand as they are way cheaper and look nice if you find a good donor. The current draw should be measure with an amp clamp and look for "Cold" current in-rush as that is peak, while continuous running is lower. Use dielectric grease on your connectors to keep the clean even with weather-pack type connectors. I think 8 AWG wire is a bit to much for such a short run, but if it matches the OEM wires, go for it.

After 28+ years as a tech, mostly dealer's, but as the elbows went, I took a contract job teaching for ACDelco and had 13 tech schools in the mid-west to teach a two day class. 6 of the classes were electrical, ending with lab scopes as EL-6. Not so much in technical service seminars but it comes up all of the time as everything has wires, sensors and serial data on it now.

I swear, someday, you'll be on the toilet and have a user name and password to get TP off the holder. Then a voice will announce "You have used your government allotment of toilet paper for this 24 hour period...Please wait 4 hours, 13 minutes for your next allotment". Can you say, black market TP?