what should the difference be between top

freshayr said
how much temp differential should there be between the top and the bottom of the radiator? i.e. how many degrees are you typically lower the temp of the coolant as it pases throught the radiator?

Good question!! I have no clue, but do know a thermostat
is helpful to slow the coolant flow down slightly.

I guess you could put digital temp sensors at the top of the intake,
and at the water pump inlet, to find out for sure.