the stock gc8 one falls over around 1.55 bar (although some have been able to clock higher)
the stock gda/b sensor falls over around 1.64 bar (although again, some have been able to clock higher)
your options for MAP sensors are AC Delco 300kpa sensors, or Texas Instruments 500kpa sensors. these are the industry standard aftermarket sensors for motec/autronic etc.
bear in mind the AC Delco 300kpa will support up-to 2bar positive manifold pressure, which makes it interesting if you plan to run that much boost, as overboosts are hard to regulate or capture without wideband.
the stock map sensor can be tricked into seeing more boost by scaling it with a pill, the only issue with this is the competancy of the tuner and the resolution of your
ECU to be able to cater to the extra loading. i would not suggest big boost on 10 row links.