What do you see as the similarities...
Without seeing both case files, it would be difficult to draw solid conclusions regarding whether or not these two unsolved murders are connected. Just looking at the limited information available I noticed the following similarities:
Both victims white.
Both male.
Both age 20.
Both military active duty.
Both enlisted and served during Vietnam War.
Both patients treated at and assigned to military hospitals.
Both on authorized leave/liberty from military hospital.
Both believed to have been hitchhiking.
Both violently murdered in close contact with attacker.
Both killed in Pennsylvania.
Both killed in 1968.
Both killed at cold time of year.
Both bodies left in the open on/near a US highway where quickly found.
Both were left with no identification.
Both victims were married, but separated.
Both had families in states away from Pennsylvania.
Both murder investigations were in the jurisdiction of Pennsylvania State Police.
Both victims were eventually identified - primarily by family members.
Both murders remain unsolved.
Both buried with military honors.
Both graves marked with bronze Veteran headstones.
A close comparison of these two murders might find even more similarities. Perhaps only coincidence, but maybe a connection?
US Route 40 in Pennsylvania might not be well traveled today (due to the newer turnpike) but it is a well maintained section of the historic National Road which stretches from Baltimore to Indianapolis.