I used my 86 4Runner with an auto and took it anywhere I wanted to go with it. Now as to doubling the auto I don't think it's possible with those years the trans and tcase are a single unit they need each other to operate properly so you can't split them. I talked with Marlin many years ago about that and he said it couldn't be done, but that was many years ago and who knows what he's done now. The trans and the tcase are full auto units and need the autotrans fluid to operate so they need to be together. The only problem with the auto is going downhill, the torque converter will go into stall at low speed so you need to use the brakes more but for rock crawling I loved my auto.