You can use Permatex Copper gasket maker and forgo the gasket altogether, just make sure you get the gasket surfaces on both the transmission and pan extremely clean and follow the gasket maker instructions exactly.

Take your old speedo o-ring off and match it up to the new one to make sure you get the right size - the one at NAPA should work fine. If the Montero is your only vehicle then take the o-ring off and measure it carefully - I.D. & O.D. - so you get the correct replacement.

95 Montero SR
3.8 MIVEC, Advance headers, 2 1/2" exhaust, Magnaflow muffler, OME shocks & rear springs, 2" body lift, 3" tank lift, 4.90s, TRE front locker, factory rear locker, Roger Brown Rock Sliderz, 315/75r16 (35") tires, Sport big brakes