Can't imagine what he modified unless he meant he ported the head (?), I can't see why they wouldn't fit the existing engine although I haven't done it myself. Probably best to rebuild the carbs it's not a difficult job to do, if you look around you'll find info on the web, I don't know about jetting hopefully it's already correct but people do the strangest things so you never know. I think a lot of these carbs came off mg maestros