Before I replaced the dizzy I would try just replacing the Photo Optic Sensing unit. If you have a junk yard around you could try to find one there otherwise Rock Auto sells them for 109.00. be careful there are a couple of different designs. There is one with the connector coming off of the side and one that has the connector coming off of the bottom. It is about a 5 minute job to replace the Photo Optic Sensing unit compared to replacing the whole distributor.
Joe