Intending to install a dual circuit disc conversion on my 64 F100. I realise you only need a residual valve on the discs if the master is lower. On drum brakes however you need to utalize a 10 psi valve to prevent air infiltration and brake drag. I know you need one as my 85 has an aftermarket proportioning valve due to my original going out. I suffer bleed back in the drums and one has to pump them several times to restore the drums to use.
I am simply curious to which side of the proportioning vlave one mounts the residual valve.