This is one that i should be able to answer and not stuff up!
Plus I am not thinking of pizza at the monent atleast for now anyway!
Lobster and 1200rallycar regarding wiring the EA Falcon alternator.
I haven't worked on a EA for a while but I am sure it is the kind with an RE60 internal regulator ( this has an injector style plug! )
If it is! you need to run power from the battery to the big battery terminal on the alternator. (1200rallycar you say on yours the electrician left the old wires! If this is so take it back and get them to put atleast 8mm thick wire for this. As to make the alternator swap wurth it , you need the thicker wire to supply the higher current if at any time the alternator has to charge at its peak! )
Now to the injector plug! If you look on the regulator on both sides of the plug will be a letter ( can't remember what side which letter is on!) One letter will be L - this means warning light from the dash. So find from the old reg wiring the wire thats runs to this light and connect to this side of the injector plug! The other letter will be an S - this means signal! This wire is to give the alternator a signal as to what the battery voltage is! On the ford this wire is only powered when the key is in the on position! You can find this wire also in the old regulator wiring! but an easier way and better way is to just conncet this to the battery positive terminal on the alternator!( Both of these wire can use the old factory wires or new 3mm wire! no larger is needed!)
( You might think this means the alternator is always on but without the key in the on position the warning light will not have power to its other side! and this is what is needed to start the regulator! )
If this is not the kind of alternator 1200rallycar is talking of! the only other one has a 005 regulator and this only needs power from the battery ( still 8mm is prefered) and the warning light wire!
( Both of these are Bosch Regulators )
If it is a different alternator to these! write what kind it is and I will try and get back to you!