I don't know about the Montero engine in this regard. However, just out of interest, I run an RX-7 MAF on my 1.6L Miata with the stock ECU, but the fuel system has enough reserve to handle the extra air at high revs (>6500 rpm)when the stock MAF would be restrictive (limit is 7300rpm). I have no problems with it. With a supercharger I guess you'll have to be careful that the MAF isn't reading at maximum before the max air flow from the supercharger is reached. Then you'll be lean <img src="/forums/images/graemlins/scared.gif" alt="" /> Might be OK at low boost.
A MAP sensor would be better if it can be hooked up to the stock ECU. A knock sensor would be good too if you're going down the FI road. Having said that I no expert on FI

'97 Montero 'LSR' - 4.6 gears & factory rear locker, 33" Procomp muds on 15x8 steelies, 50mm coil spacers, T-bar crank, Airlift, sans rear sway, 50mm rear frame & fuel tank lift, Aisins, ARB front bumper + 10k lb winch, 50mm DIY body lift, rock sliders, cut rear quarter panels...