5000 sounds crazy high. The TW could survive high revs for a long time maybe, but it's very buzzy. Your torque is in the lower-mid register mostly. 1st gear will pull almost anything. 1000km is a dandy trip, but backroads are more fun and more friendly to the Tdub. You can do a good amount of carb work (in close quarters) by loosening the carb, removing the cables, and turning it sideways to remove the bowl. There will be spills though. Look into a Dial-a-jet system if you're that worried about changing altitudes. You have to climb a few thousand feet before there's really any change in performance.