I've a right hand gear lever on my right hand drive vintage trike and to be honest - it was the least difficult control to adapt to using. (The usual for right hand drive is left hand gear lever).
Throttle - hand lever on steering wheel Advance/retard - hand lever on steering wheel (these days, fully automatic) Air - hand lever on steering wheel (these days, also fully automatic) Brake pedal - rear brake only Handbrake - front brakes only
The hand controls actually are pretty easy, the difficult bit is the brake operation. Many vintage trikes are converted such that the operation is the other way round.
The hand controls are also made easier by the fact the steering is only 270 degrees lock to lock. (Early trikes are even less, 135 degrees or so).
