The first year for the side mounts was 1958. So, if your motor has 3 bolt bosses cast on the side of the block then it's not a '55 motor.
Trucks in the 40's and 50's all had front mounts (at the harminic ballancer) and rear side mounts on the bell housing.
What are the casting numbers and serial number (stamped on the machines surface next to the distributor)? These will help ID what you have.
Mike B
