I am getting supplies together to replace the master cylinder and all the hard lines on my '64 2wd with drum/drum. I see replacement kits in 1/4 and 3/16. Which came from factory and is one size preferred over the other. I will be using a dual chamber master cylinder if that matters.

 

Definitely not 1/4".
The rule of thumb is the larger the line, the harder it is to bleed.

 

All 3/16th Mac.