What crank are you going with?
They made 80 and 82mm WBX cranks. At least Oettinger made them.
I will be running a 80mm waterboxer crank in the engine with webcam 86b camshaft, latest version of the los panchitos head, 5.6 inch H beam rods, 9.6:1 compression ratio, 48mm dellorto trijet carbs (37 vents) and 1 5/8 exhaust system. I am planning to make 170HP with this engine.