Small block crankshaft endplay

I'm gonna go on record as saying there's no way to have 1/2" end play. The engine would stop running before that much metal could be worn away.

The auto trans pump cannot place any axial load (thrust) on the crank. There's is no reason for the pump gear to thrust - it's an even 'cut'. Even if it did, the drive tangs on the converter snout would simply compensate.