Anyone looking to change from power to manual, drum to disk, etc. please take a minute to look thru here(and the rest of mpbrakes FAQ section):
http://mpbrakes.com/mpfaqmasters.htm
They have a ton of info, all about pedal ratio/bore diameters/valving etc...I have always turned my own rotors, done my own brake work, but after reading this stuff, realize how little I knew about brakes.
The 65 galaxie has 5:1 pedal, so dual circuit drum conversion needs 1" bore master for decent pedal feel- so it says. Luckily the one I bought was 1", and had the residual valves built in, but was just luck. now I know it should work.(was single circuit power drums, converted to dual circuit manual drums). One thing I didnt like, the pedal was too high if pushrod sized for full stroke before hitting floor- ended up taking 3/8 off (4 7/8 now -hole center to end) to get pedal back to normal released height. when bleeding one circuit, other still built pressure, so I'm pretty sure travel is adequate if one circuit fails. havent driven it yet, will post update to say how brakes feel once its on the road- very close now, week or two, but wont take it out until rain washes salt away...