I made a tool to do my 1989 MK1 Pajero (i'm assuming that's the same as a Montero), it's fairly easy to do if you have access to welding gear.
The dimensions for the tool is 60mm between dowel centres (i used M10x90 bolts with the ends ground down to fit the holes) I used a bit of box section approximately 40x15mm 120mm long and welded an old socket to that. Sorry the dimensions are metric.

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