[Dave in MN]

From my experience, you will need extra cooling capacity if you are planning to fully use the extra power available from the engine as you are building it. Be careful in the selection of your cooling system as the possible result of overheating a B block is a crack developing between an exhaust seat and either the adjoining cylinder or intake seat. I suggest you consider a 4# pressurized radiator.
I have experience working with many cooling systems for Model A's. A well maintained stock engine used/driven as originally intended will only require a stock radiator/cooling system. When you start producing and using more horse power, more heat is produced and it needs to be extracted from the engine.
I have two 4# pressurized systems in my touring cars with Brassworks radiators. One engine produces 65 hp and the other produces 80 hp. Both engines are pushed a bit on the freeway occasionally and without the sealed systems, they would throw water out the overflow tube and overheat. The engine you are describing is very close to my 65 hp Phaeton engine.
FWIW: I have heard nothing but good things about Berg's radiators. I met the owner in Branson, during a national convention, while walking through the swap area and looked his product over. His workmanship was very good.
Good Day!