another cabinet question...sorry

here's the deal my friend want's me to build him a new 4x12 cabinet because the one he's got is about to fall apart and sounds pretty crappy. I was going to go with a 32" x 32" x 14" square cab. use 3/4" birch plywood, and 1" x 1" bracing. He wan't me to use the same speakers which I'm pretty sure are celestions(since it's an old marshall cab). When I wire them, should I mimic how they are currently wired and use the same jack or would it be that much harder to wire them like the marshall 1960 cabinets where you can switch fro 16ohm or 4ohm or 8ohm stereo. If he really want's to go that rout where could I find a jack that supports that type of wireing. Any help will be greately appreciated. I know this type of question has been done to death so I will be happy with any links that will get me headed in the right direction. Thanks again.

If his cabinet is real old like 70s or back he'd be nuts to take it apart as its worth money.
As for the cabinet I'd go by the same exact dimensions,wood type as a Marshall cab.Also there straight cabs aren't straight the face that the speakers mount to is angled in the cab.
Marshall used Celestion speakers(I prefer the 25watters cause there smoother)Wire the two left speakers in series positive from the jack to positive on the 1st speaker out the negative into the positoive of the 2nd speaker then out the negative to the negative poll on the jack.Then just do the same for the other side.Wired like this 4 16ohm speakers=16ohm cab.
As far as the stereo-mono switch unless hes splitting his cab with two heads just stick the single jack on and be done.