I don't see John in NamUs and I'm throwing this out as a Hail Mary since the deceased has a tattoo that says "Jack". Post mortem pic at link.
What about
The National Missing and Unidentified Persons System (NamUs)
Unidentified Person / NamUs #UP7958Male, White / Caucasian
Date Body Found March 13, 1993
Location Found New York, New York
Estimated Age Range 60-80 Years
Circumstances:
Unknown white male was witnessed to collapse on a northbound A train at the 125th street station.
Tattoo of an eagle on right forearm, tattoo of Native American chief on upper right arm, two multicolored tattoos on left arm, depicting military designs with stars and "1948"and "1949" "Jack" "Good.....For......"