According to 1929-1954 Chevrolet Master Parts book, the 51-52 Master Cylinder has the number 341 stamped on the Master Cylinder followed by the letter "H". The 53-54 Master Cylinder has the same number stamped on the Master Cylinder followed by the letter "J". However, the 53-54 Double Duty also uses the same Master Cylinder as the 51-52. That Part Number is: 5453837. The Part Number for the 53-54 is 5454022.
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