Just poking around the internet a little bit, I found this at http://www.landscaper.net/discharg.htm#Upgrading%20Discharges
Upgrading Discharges
Over 400,000 veterans who received "less than honorable" discharges between 1964 and 1973, may be eligible to have them upgraded to Honorable. (This does not include Dishonorable or Bad Conduct discharges)
Postal applications:
Joint Liaison Office
Attn: Army Liaison Team
USARPAC
St. Louis MO 63132
Phone calls:
The Joint Liaison Office 1-800-325-4040
Alaska, Missouri, Hawaii, & Puerto Rico 1-314-428-3500
National Personnel Records Center - Military Personnel Records
This could be real interesting.