I could routinely tow 3500 - 4000 pounds over 100, but mine was turboed. Originally mine was much like you describe, it made hills seem like mountains. There are others whom could cruise just fine and get decent gas mileage.
Those that have swapped to a turbo engine have little interest in going back to the carb. Power and mileage improve greatly.
I just put together a stock 5 speed that I use for snow plowing. I am already thinking i want a different engine, not sure if it will be a 2.4 or a V6. Maybe just fuel injecting the 2.6.

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.