only 96+ mustang require o2 simulators because of the OBDII emissions systems. 95 and down mustangs still have OBDI systems and do not have o2sensors downstream of the cats.

It would be better to just buy and off-road h-pipe though. If he still has the stock h-pipe it is only 2.25" piping where as an aftermarket h-pipe is 2.5" to 3".