1966 dual master cylinder

buzzkill had a later model duel master cylinder conversion on his car same as you are doing, if the mastercylinder fails duel reservoir isn't going to help, but if a break line or wheel cylinder fails a duel reservoir will keep you from losing all your brake fluid and keep 1/2 of your brake system functioning so you can slow down or stop

also a good idea to make sure the EMERGENCY BRAKES are in good working order, in case of an emergency
the most common problem with the emergency brakes are old stuck rusty cables so it is a VERY good idea to replace them if they are old, new ones are about $15 each side and you can find them everywhere (it is a good idea to take your old ones with you to make sure they give you the correct ones)
Mine does work, But I used it a couple of times and I had to unfreeze the long cable =D>

I used the plastic top metal bottom style master cylinder, ran the rear line straight off the master and ran the other line down to the distibution block used the distribution block as a splitter for the fronts....I also ran all new lines.... Gearing up for the scarebird conversion as 9 inch drums don't cut it in todays traffic....
Did you have to add an adapter plate and use a different push rod ??