83cheviac

I have swapped my entire v belt system in an 84 pick up with a 5.7 to the serpentine style from a 94 model. My old alternator has a thicker gauge wire and different connector plug running to it vs. the thin wire and new connector which is used on fuel injected 5.7s early 90s. Can I simply splice in the new connector on to the existing alt cable? Because I have seen cases where the old wire is eliminated and a wire matching the gauge of the new style plug is selected from the harness and substituted in. If I choose to substitute a new existing wire from the under hood harness (because I have many extra hangin out) what should my multimeter read or how do I find a suitable wire?? Hope this makes sense