"In fairness, how many 55's still has original master cyl. and booster?" I would think most 55's still have the original master cyl. and booster as the Kelsey Hayes was a one year application. Last time I checked the kit was $125.00 advertised in the WPC Club magazine. The cause of failure lies mostly in the diaphragm in the booster. Some may say, the 56 power brake system will replace the 55. I would not disagree but have no knowledge of that being done. Jim M. 1939 Custom Imperial Limousine C24