The photos of the modified version has been posted on this board, possibly by Jim, the more holes the better of course and its a balance between leaving a hole big enough for large items to enter the oil pump return side and small holes being blocked. I have bought a sump plug for a 12mm hole with a magnet and will drill in from the bottom so the magnet fits inside the hole extended horizontally from the other crankcase and extend a bit further upwards, this will give better protection and allow inspection of at least one of the small holes to check if it is blocked plus hopefully trap even smaller pieces. Why Norton did away with the large sump nut on these 72 crankcases is a mystery, but not enough meat left to reinstall it so you are left with making do.