I started on my LJ with single diaphragm booster, standard LJ master with WB front calipers on VN disc's & VL disc & caliper rears.
Brakes were crap.
Pedal didn't hit the floor but went bout 7/8 the way there & pulled the car up pretty ordinary, definitely no major improvement over LJ disc's.
After much rebleeding & head scratching i finally crunched the numbers on caliper & master piston sizes.
Basically the master was same size bore as a VL but the WB caliper has a piston with approx 25% larger surface area than the VB-VL caliper.
I found a set of VL calipers & drilled the front adapters to suit.
Greatly improved the braking ( then you can go faster then you want better braking )
I put it down to basically the fronts were taking the bulk of the fluid but with not enough pressure to make them bite hard enough before the rears then did their bit.
Hope this helps