Master cylinder for Power DRUM brakes

My '68 Torino GT has a 390 GT motor and four wheel DRUM power brakes. The P/B booster is leaking as is the back of the master cylinder. It appears to have a disc brake MC on it (front reservoir small, large rear reservoir) While talking to the brake expert at ChockStang yesterday, he claims my car should have a MC with two "same size reservoirs" with residual check valves in each port. The front port must point down due to shock tower clearance issues. Does anyone out there have a photo of an "original" Power Drum brake MC? I can't locate anyone that has a good core that could be rebuilt. Any help would be greatly appreciated. Ya, I know, a well optioned GT should have front discs on it but....