Dodge flathead six crank pulley

[olddaddy]

I am building a 46 Dodge WC to somewhat original specs.  However,  I want to use two row, 3/8" belts on the crankshaft, water pump and alternator.  I've heard some of the later cars and trucks with  bigger engines had them.  I've also heard there are hubs with bolt holes to attach pulleys.  And possibly a later V8 or Slant/6 pulley would fit.  The bore is 1.5" X 6.375" diameter.  Anybody know about this sort of thing?