Here are all of the solenoids. The Fuel solenoid is attached to the alternator with the left bolt of the alternator bracket. You can also see the two prong connectors that I used to connect one wire from the fuel and one wire from the nitrous solenoids to make four wires into two wires.
Mustang Tech
Install A Nitrous Express System
Here you can see where the fuel solenoid attaches to the alternator bracket.