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Today, I started on what I hoped would be the straightforward job of rebuilding the brake master cylinder for my 70 Z. Disassemble, clean, install new seals and hardware, and reassemble. Job done. What could go wrong? Unfortunately, I only got to Step 2. After cleaning things out, I found a little divot in the floor of the cylinder bore, located about 1/2" aft of the rear stopper bolt. Hard to say what cause it. The car has been sitting for many years so I guess it corrosion damage. It's about 1/8" in diameter and deep enough to catch my fingernail on. The rest of the bore is in great shape. When I look at the cross-sectional view of the Brake MC in the 71 FSM, I see that this divot sits pretty much mid-way between the front and rear seals of the rear piston. Knowing that, it doesn't seem like the seals stand a chance of being nicked by it. Nor do the rear piston and seals that came out of the cylinder look like they've been hurt by it. So - Question 1: Can I get away with just leaving it as-is? If the answer is that it's going to be ok to ignore it, then I've still got a minor problem in that that the rebuild kit that I bought a number of years ago is not suitable for the 70 - 71 brake MC -- different seal types (even though the bore is the same). That leads to... Question2: Anybody know where I can get a rebuild kit for the 70-71 MC? If the answer to Question 1 is 'MC must be replaced', then I've got a much bigger problem. The 72 MC, while an improved design, has the front and rear reservoirs and lines flipped around -- which means that my hard lines won't fit. Plus, a 72 MC would dilute the 70-ness of the car's engine compartment (a small but touchy consideration). MSA lists the early-design Brake MC as NLA. The typical parts suppliers also show 'NLA'. Then there's Rock Auto... Rock Auto shows NLA for 70, but lists two units for 71. One is from Cardone, the other from Centric. When I look at their 72 listings, there are about 6 choices, including Cardone and Centric. The 71 and 72 Centric units have the same PN, so that one's undoubtedly the 72 design. The 71 and 72 listings for the Cardone units, however, show different PN's. In addition (although this may mean nothing), the pop-up picture of the 71 Cardone unit shows the 70-71 design, with the 'F' line/reservoir at the front and the 'R' reservoir/line at the rear. Question 3: Does anyone have any experience with the Cardone unit listed under '1971' from Rock Auto? Could it possibly be the real deal? (i.e. the 70-71 design). If these 70-71 brake MC's truly are NLA from anywhere, what do members recommend as a remedy. Am I really going to have to fit new hard lines? or... Question 4: If I am forced to fit a later-style 72 MC, does anyone know if I can install the internals from my 70 MC into a 72 casting , thereby keeping the reservoirs/lines in the correct, 70-71 orientation? Both castings have a 7/8" bore and -- other the placement of the stamped 'F' and 'R' markings -- I think they may be identical. Intuition suggests that the factory would have made efforts to keep the same casting when they upgraded the design, limiting the changes to the internals (and the hard lines).