The SR calipers and discs are wider than the gen1. The 3.0 Monteros and all the 90's Sports have direct swappable calipers with the same width discs. These use the same AP530 pads as 3000GTs, G VR4s Diamantes and other Mitsus so it is easy to get many compounds of brake pads.
I just swapped Sport calipers onto my MM and eliminated the rear axle valve. Only test driven at this point but I think I like it.

Cheers, Charlie
If It ain't broke, Modify it!
87 Montero turbo Converted back in Spring1989
95 Montero SR 3.8 DOHC Only one?
93 Pajero 3 door 6G75 Mivec with paddle shifted 5 speed
Then a Gen2 SR with full coil independent suspension.