Hi, Just received the MGB/C Stalk Caps for 1968-1980 part #141-775. I got them in Stainless Steel to replace the original black to dress up the cabin alittle. Was able to unscrew the old caps from the stalks without problem, but cannot pry off the old caps from the threaded plug. I followed the instrutions using a screwdriver, put cannot get them off. Any tricks to this?