[GC427]

I checked the 80 amp fuse by taking it completely out of the circuit. The ohm meter reads 0.00 ohms. Therefore, not a blown fuse. Sorry for the poor photo, as you can see there are 5 red wires on the left side of the fuse and 2 red wires on the right side of the fuse. SP03033, you mentioned has 6 wires on one side and 1 on the other.

How would one verify the voltage regulator is working correctly?

If the alternator is producing 17.5 to 18 volts, was the wrong alternator installed, or is it now malfunctioning?