My 64 malibu has standard drum brakes, and the unsafe single master cylinder. What is the easiest (cost is a factor) way to convert to a dual master cylinder? I plan on keep the stock brakes for now. This is just an occasional driver, but I want it to be a little safer. The car does not have a booster, and I don't plan on adding one. What donor cars would I need to get the cylinder from? Do I need to change/add a proportioning valve? thanks for the help in advance!

Troy,
you don't need a prop valve.
get a M/C from anything GM. 67 on up.
you will need a M/C with a deep hole in the back of the M/C.(manual brakes).
follow your brake line down. it should go to a distribution block.
disconnect the rear line and plug the distribution block port that the rear line went into.
the original brake line will go into one port on your new M/C.
get a length of brake line, same size as the rear line, and a union, and extend the rear line up to the M/C.
bench bleed the new M/C before you install it.
bleed your system and you are good to go.
david


p.s. you may need some adapters for the lines to the M/C.
here's one that should work...
http://www.partsamerica.com/ProductDetail.aspx?mfrcode=A1C&mfrpartnumber=101505&parttype=230&ptset=A

Troy,
i had a 62 impala, years ago. that i added the dual master.
a friend had a 60 bonneville. i wanted to add the dual master to his car and he said, "someday".
well, his rear wheel cylinder failed and he almost went thru his garage.
we put the dual M/C on the next day.
david

p.s. you may need some adapters for the lines to the M/C.
here's one that should work...
http://www.partsamerica.com/ProductDetail.aspx?mfrcode=A1C&mfrpartnumber=101505&parttype=230&ptset=A

Or go to your parts store. Many of them have assortment boxes with fittings and adapters. For example, they have them at our local Autozone.