We have an early model 3VW engine. It came with a Walbro carb, which required a fuel pump (also provided with the engine). We decided to remove the Walbro and put on a Mikuni VM26 carb. (possibly VM26-606, not positive)
The Walbro was mounted in an almost vertical orientation. To mount the Mikuni, we had to modify the intake plenum on the Verner to allow the Mikuni to be near horizontal as related to the engine. The Mikuni is gravity fed from the wing tank with an inline fuel filter.
Works great.