I don't think you want to do that. I think it will mess up the air flow. Also the fan blades may flex a bit and rub on the radiator.
I think your best path is to move the radiator forward. You're going have to modify the radiator support. Maybe you can cut some slots in the top of the support so you can drop the radiator mounting flanges in front of the support instead of behind it. If can do that you can use washers or something space it.
I'm only trimming the shroud where it contacts the frame of the rad on each side. It will contour to them and make it so the fan can sit flush on the fins of the radiator. Should actually help flow. If that doesn't create enough clearance I will cut the mounting flanges off my new rad and have a friend of mine weld new ones on to push the rad 1/2" forward.