What year for those cars are you looking at? Obviously anything 55-66 is going to be a single reservoir/single piston unit.
67-68 Chevelle/Nova/Camaro should be the same and should be good for your application. Not sure why the Impala wouldn't be either.
I'm assuming from your other posts that this is a no booster deal for drum brakes.
A drum brake m/c for the above cars should have residual valves but some rebuilds don't have them. You need them if it's drum brakes.
All 67-68 Chevelle/Nova/Camaro master cylinders should also have the deep cup for the pushrod, whether they are power or not.
67-68 Chevelle/Nova/Camaro should be the same and should be good for your application. Not sure why the Impala wouldn't be either.
I'm assuming from your other posts that this is a no booster deal for drum brakes.
A drum brake m/c for the above cars should have residual valves but some rebuilds don't have them. You need them if it's drum brakes.
All 67-68 Chevelle/Nova/Camaro master cylinders should also have the deep cup for the pushrod, whether they are power or not.