Make sure you've got 1/2" clearance ALL THE WAY AROUND the fan- The engine doesn't really sit square to the radiator, so take nothing for granted. Last thing you want is what appears to be 1/2" at the top, and 1/8" at the bottom... and since the diameter is probably larger also, check VERY closely at the top and bottom tanks (and trans cooler lines). If it's close near the tanks, remember that the engine moves...
If you've got 1/2" minimum everywhere, you can probably go with it. I usually like to see 3/4-1" minimum (or whatever it takes to put the fan half in, half out of the shroud), but sometimes you've gotta just call it good.