I put 235,000 miles on my '91 Montero. Sold it in 2009 due to rust but it still ran good with excellent Michelins on it. It went to a good home and the guy who bought it drives it daily. The '99 Montero is a definite step up from the '91. Had to put Bilstein shocks and John Baker Performance Products heavy duty springs on the back of the '91 to keep it tight. The '99 has hydraulic adjustable shocks. The '91 3L engine was underpowered. The '99 3.5 L 24 valve engine takes care of that. Larger wheels on the '99. Intended to have my 16-year-old drive the '99. But while driving it the 430 miles home from the dealership I had to keep it and find her something else.
3 L 24 valve engine, hydraulic adjustable shocks, suspension, 13 grease fittings on the front end just like the '91, rain gutters, super grade leather seats, final year of the platform with bowed-out fenders around wheel wells and integrated running boards functional to keep debris down.
Make the third row jump seats easily removable (not just flip up to the sides) for maximum cargo capacity.