Kelly,
If you know your father's full name and DOB, I would try to order a driver's licence search. You may be able to get his current, or his latest known address. Also, you might want to go to see your county clerk to do a search for marriage records on him. From this, you will be able to have his Social Security Number, and also address, DOB, and permanent address of the couple at the time of marriage.
Basically, as you go along, this will open up other pieces of information.
Voter Registration Records will also give you a valid mailing address.
I once went to a seminar given by Ed Pankau, a PI from Texas.
www.pankau.com
It was the best money I ever spent!
I would also try contacting each Fraternity's National, as they would have records of each man who pledged and in what year he did so. If you can narrow down to a 5 year span when your father would have pledged at his specific chapter, they should be able to find him. You would have to talk to the Historian or the Archivist, most likely.
Good luck to you!
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