Dual pot MC conversion- differences for Frame rail installs

[Rambow]

I'm tearing into the brakes on my '53- going to replace all the lines, hoses, etc.
This is just a stock redo- just 4 wheel drums, no disks, no power.

I ordered up this conversion bracket so that I can switch in a dual pot MC for safety.

http://www.ebay.com/itm/161135059309...84.m1497.l2649

I read the sticky thread in the other forum about the conversion- the overall plumbing is straightforward- but I have a question about these "residual valves"

It sounds like a stock drum/drum MC HAS residual valves built into it already (required for drums to lightly hold the shoe against the drum)... but then I read that you needed an additional ? residual valve if the MC was going to be down on the frame rail to keep fluid from backing up? is that right?

Can anyone clear up what is needed plumbing wise for a basic drum/drum dual pot master cylinder mounted on the frame rail of a '53?

Thanks-
Ben