I'd be real suspicious that the compressor has a problem. Before you invest in a clutch, you really ought to have somone put a set of guages on it to see if there's any refrigerant. Here's a typical scenario - the freon level drops due to a leak, and since the lubrication oil is carried in the freon, the compressor runs without adequate oil. Due to age or lack of lubrication, the compressor piston seals fail, or the compressor develops a knock or rattle. The low freon level will deactivate the system to protect it, but a basic truth is this: if the A/C system has been inactive for very long, you need to be prepared to make a comprehensive repair to ensure proper function and to avoid wasting money. You may be lucky and just need a shot of freon and a switch, or you may waste money putting a clutch on a bad compressor. What I'm trying to say is, with AC work on older vehicles, it's rarely a simple cheap fix. Just be prepared, and don't get disappointed if it's not the clutch.