What type of fan do you have? If it is a flex fan, make sure that it is not a reverse direction fan.
1 1/4" is too far away in my opinion, especially since your fan extends significantly below the bottom of the radiator. When the fan extends below the radiator, it will draw air from below the radiator rather than through it.
I have seen trucks set up like yours work jut fine, but they did not have a 1 1/2 inch gap between fan and radiator. I recommend a 1/2 inch gap.
Carl
