Some suggestions based on my experience:
1) Check with Denny's on antenna suggestions:
http://www.dennysantennaservice.com I've had really good luck with him and felt I got the straight scoop.
2) The satellite mount may not work straight out. You may not find a piece of pipe that will do the job. Make sure to check that out. You may also need more heighth.
3) Last I checked the analog to digital boxes were something like $50-$60. Given the prices of TV's now that are all digital you really may want to look into replacing the old TV. There are some terrific prices and you will be much happier with the picture and setup.
4) How far are the towers? Have you considered using rabbit ears instead of an exterior antenna? It might work.