leme ask this first, how restrictive did your blocks come out?..... you probably was surprised at the amount of flow you got....right.
I would split the paths to each block from the radiator, have them completely separate right back to the reservoir, and then add the pumps in each of those lines,
make sure the line between the reservoir, and the radiator can handle the increased flow. That would also be where the flow meter would want to be.
as per usual, make sure the pumps are in the lowest part of the loop, so as to prevent airlock.