ticking like a sewing machine

You didn't buy that Duster in Central Pa by any chance did you? I know a guy that sold one around November and the discription/BS sounds familiar.
Two good points already brought up, you need to track down the tick a little tighter. Pull the valve covers and look for loose rockers, if you haven't already, see if you have adjustable rockers...plus you'll get to see how "fresh" this engine might actually be. Let us know what you find.