1157 is a dual filament bulb. You need two single filament bulbs.
You say the 1156 won't fit in the socket. I don't know what the difference is in the stud placement on the bulb base between 12v bulbs and 6v bulbs but is it possible that your taillights have 6v sockets and that they won't accept 12v bulbs?
I don't know. Just speculating.
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
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