The current draw if for the original cooling fan is 6.5 to 7.5 Ampers when running,
at starting it can draw up to 25-30 Ampers for 0.5 seconds.
9 and 12 inch fan draws almost the same. As the diameter increases, the strating
current needs a little more time to drop.
The fan supply wire thickness is very important. Too "thin" wire can set itself on fire.
High starting power drain can be eleminated with PWM fan control modules, they provides
soft starting and speed control proportional to engine temperature. No need for fan relay(s)
when used. The PWM module can use the engine temperature sensor's signal.
With PWM modules you can save electric and engine power (and some fuel also).
An other, cheaper, but automatic solution is to get a double thermal contactor from a turbodiesel 33.
(Aftermarket contactors are also available in different cut-in temperatures. As i know the thread size
is matches with the petrol version, but it's need to be checked.)
This double thermal contactor is able to handle two radiator fans.