What DynoMax ST Muffler Size do I need? Offset?

[FiveOhhStang]

Im about to purchase two DynoMax Super Turbos, what size(2 1/2???) and what kinda of offset or center do it need? Link to maybe the Summit one that would be correct for A STOCK MUSTANG would be aprreciated, im totally stock exhuast wise to headers, nor aftermarket h or x pipe.
THANKS!
-Nick