Headwork, cam, refurb the rest of the head, 3 angle valve seats and you'll be laughing. Though is the oil loss through the stem seals or from bypassing the compression ring on the piston? Be worth figuring that out first.
Good gains from porting these heads well, same with the 16v and even if you dont cam them. Second hand cams are cheap as chips though so might as well be done! We've built lots of mad spec 8v and 16v's, they can be turned into right monsters haha