RockAuto list wheel cylinders as 13/16" but say for 770 and I think mine is model 170 (rubber floor mats seem like the base model)
The fronts are listed as 1" but again say model 770. Is there really a difference from a 170 to 770 on brake stuff?

Also would like to change to dual master cylinder. Will 67 Dart bolt in? What about rod?

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76 Dart

As advised in your other thread: pay no attention to RockAuto's silly claim that the vehicle trim level has anything to do with the mechanical parts. It doesn't.

The dual master cylinder swap is a very good idea. Get a new master cylinder, don't futz around with "remanufactured" garbage. If you're staying with drum brakes, use a Wagner MC71258, Bendix 11323 or Raybestos MC36221. If you're swapping to (any kind of) disc brakes, use a Raybestos MC36412. These will bolt right in place of your existing single-pot master, and your existing pushrod and pedal will work. You'll need a distribution block/combination valve; buy it new from Inline Tube here. You'll need to run dual hardlines from the new master to the valve. Be sure to bend at least one fully-circular loop in each of them to let them flex as the car moves. Steel line is standard and is a pain to work with; Cunifer is a lot easier (and better). If you're putting in (any kind of) disc brakes, you'll want to install a holdoff valve in the line to the rear drum brakes to avoid rear brake lockup; that's this one.

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