I just purchased a new probillet distributor for my 1987 5.0 project. this engine has a billet steel roller camshaft and the problem is that the engine is now carbureted instead of fuel injected so i ordered the distributor with vacuum advance. this distributor comes with a cast iron drive gear that says it cannot be used with billet steel roller cams. im starting to get frustrated with finding a shop that can properly install the new gear without damaging it or the distributor. does anyone know exactly how crucial it actualy is to change it or the proper way it is done?