Intercooler fan yes or no ?

[Winnie]

G'day Craig, I'd say it depends on the intended truck usage mate. If it were for highway use then I'd imagine the scoop would do all the work needed. I'm thinking for low down slow crawling applications a fan would near be essential to stop heat soak on top mount IC's.

I agree with what MB says here. In fact at highway speeds or even general road speeds, a fan is more of a hindrance than a help.
But offroad at speeds below 40kph then fan does help a fair bit then.
I have a fan on my cross country cooler wired to ignition so it is always running. I would forget to switch it on at low speeds if I had it on a switch, and I think it helps with heat soak when stopped at lights etc, it always has cooler outside air flowing through it so doesn't soak up as much heat from the engine.