Your F53 460 is not OBDII. Contrary to common opinion not ALL vehicles went to OBDII in 1996. There was a Gross Weight exemption that Ford took advantage of so the F53s didn't go OBDII till the 1999 chassis.
So you'll need the old Ford-specific OBDI code reader and the connection is under the "doghouse" engine cover. Look to the upper Left for the connection.
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Pic stolen from Subford)