Hey Adam, I'm doing the reverse-ish in the Duster. I have 4 wheel power drums, looking to disk up front, a mastewr swap is coming. I ordered a power disc master from Auto Zone. Rebuilt unit. $25
Depends on how hard a pedal you like - Power brakes have a different length pushrod (you know that already) and have a different pedal ratio. It takes less pedal movement to provide the same amount of brake pressure on a power assist brake car.
So, if you like a hard pedal, use the existing pedal assembly and replace the master and get a new adjustable push rod.
you really sure all that is less expensive than a new booster???
A quick check on www.rockauto.com shows A-1 CARDONE Part # 5476206 available for $118.79 - This is a rebuild and return service so you will have to send your existing booster in and then get it back. Only real difference will be in the finish - it will come back painted or bare, not cadmium / zinc plated.