My Dad has an '84 or so G-wagon 5-door that he's owned since new. I don't think it would hit 80 falling off a cliff, if it did you'd have to shave by the time you got there. The truck is SLOW. He drives his a good bit and is considering adding a turbo. He lives at 7,000ft though so elevation does impact performance some, but even at sea level it's SLOW.
That said if you lock the diff's and put good tires on it, it'll climb Mt. Washington in 2 feet of snow.
If you're commuting on I-95 daily it's probably not the best choice. If you're doing non-highway commuting it'll do everything you want it to. Might just be slower than desired. The seats are really uncomfortable for any long duration driving.
These guys are who he has used to service his truck.
Europa G.Wagen - Home