The master cylinder was replaced on my 1965 Mustang today. It corrected the leak but my power brakes did not return which the mechanic then traced to the brake booster. It seems nearly impossible to find a booster for sale on its own.....always sold with the master cylinder but a master cylinder is readily available from many part sources on its own. The price to refurbish a booster is quite dear but seems to be my only solution. Any other suggestions out there??