The information I have is from the ICCA Judging Manual for 68 & 69 B-body, if that is something you find trustworthy.

B41 & B51 option

"The master cylinder is a dual reservoir design manufactured by Bendix. The master cylinder is painted semi gloss black."


"All cars equipped with power brakes, option B51, have a power brake booster. The power brake booster is painted semi-gloss black in 68-70 and yellow zinc dichromate plated for 1971-1974."

Is drum brakes an exception that is not referenced here? I may have missed something.