Dont think you would be able to re-use the old ones on the chain stays, Would loose to much material cutting/grinding them off. Time you source new lugs pay someone to do the work and repaint the frame.
You would probably be best of buying a new frame and selling the old one unless you have some sentimental attachment.
Does it have a brake bridge on the seat stays with a hole? You might be able to fit a U brake plate adapter