fan swap - wiring...

Well... your stock fan is setup for low speeds and high speeds. Your aftermarket fan is set up for one speed. It's not compatible. You can hook it up to the low speed or the high speed... Or you can re-engineer it. What else do you want?

Check out the following post. This guy is wanting to do nearly the same thing.

Can't make it so that a 5yr old can do it and still be stock. Afraid some work is going to be needed.

http://www.stangnet.com/mustang-forums/823790-mishimoto-cooling-fans.html

However, since you have a single speed fan, it might just work to tie the LS and HS wires together and wire straight through to the single speed fan. (feedback may not be an issue as mentioned in the post).

Depending upon the wattage of your fans, this may blow the low speed circuit breaker. If it does, look at the part about a ballast resistor. Another option is to jump the LS fan circuit breaker with a piece of wire.