Tim,

There were not "offset ends" on 1954 A-D 3100 mufflers.
1954 muffler - no "offset" ends
straight-through design

"offset" ends on 48-53 mufflers
"offset" ends on 1947 mufflers
reverse flow design

There were not "offset ends" on Early Task Force Trucks 1955-2nd mufflers - no offset ends (straight-6s and V-8s)
straight-through design