pulling the cab
just to verify a number you already have stamped in steel??
don't count on finding a number under the cab - 55 was when they started stamping the vin on the frame and it was inconsistant until 57 or later, some 55's didn't get stamped, some had one, same with 56 and 57, varied at different plants .... and not a matter of
"could be" correct, plug the number in
the vin buster 
Bill
