On my kids' '65 fb I used the Trans Am Racing kit to swap out the jelly
jar 4 drum setup for a 2-pot pdb.  The prob with a 2-pot and a booster
in a '65-'66 is the lack of space between the firewall and the shock
tower.  TA addresses it with a CNC spacer between the booster and the
firewall.  NPD and others have a booster with a sheet metal bracket
which apparently does the same thing.

With the TA spacer, first you mount the booster to the spacer then you
thread four studs into the spacer.  These studs go through the same
holes as the pedal support uses.  The pedal support attaches to the
firewall with bolts from the engine side that thread into welded
inserts on the support.  The TA studs go through these threaded inserts
and are retained with nuts from the passenger side.  I had to run a
drill bit through the threaded inserts to get the studs through.  I did
not destroy the threads; just increased the inside diameter a bit.  The
nuts required a U-joint and two 12" extensions to get to them.

The TA kit uses the SSBC 4-piston disc and caliper assemblies, very OE
looking.

I used the prop valve that came with the kit.  I am unhappy with the
pedal firmness.  I intend to put a 10 psi residual valve into the rear
circuit to see if that will help.  Check Master Power Brakes web site
-- they say NEVER to use a prop valve.

180 Out