1989 F250 4.9L running rough

My husband has an 89 F250 with a 4.9L engine. When he bought it, it was running extremely rough. He has worked on this thing til he is totally flabbergasted. It acts just like it is flooding out, it runs rough and just acts like it is getting too much gas. Anyone have any ideas? Thanks so much

timing is probably off. check ignition timing