Pharg55

You say that you are measuring 11.4v at the alternator, is this the same as you have at the battery itself? If so, this is pretty low for a battery, so try trickle charging the battery off the car, and then see how the alternator performs. It would be unusual for a replacement alternator to be giving the same problem.
Check the wiring diagrams on this forum to see what wiring goes to the alternator. See community/downloads