Genedn, you might like to view the post Crank case Inspection. I havent stated it specifically yet, but you will see shortly from the pictures that my design criteria for the Norton gearbox hook up on these chopped cases was in fact to have standard Vincent swing arm position dimension & be structural enough to have a standard RFM & UFM built around them. I have 1 engine destined for an Egli replica frame I have built the other for "standardish" Vincent components.