Pulley Diameters

Not trying to hijack C but chasing a "similar problem".
Rob what is an accepted difference/variance?
I checked factory service manual cooling section ....nada...smallest section in manual lol.
Have you got an infrared temperature gun? Shoot at the upper radiator hose JUST off the thermostat housing and then off the bottom hose RIGHT off the radiator. See how much difference there is.
Sorry for hijack