With the Fluidyne radiator you can use the STOCK air box without modifications or relocation (contrary to the instructions that came with it) My stock radiator was corroding and leaking so I replaced it.
From memory
*cut off the 2 center bolts from the radiator as they don't match up to the fan
*bend the small 1/4" hose outlet down
*trim a small section of the fan shroud around the large radiator hoses to get it to fit
*Put the radiator in the car WITHOUT the fan attached
*Cut slots on the fan shroud where the bolt holes go. You want to slide the fan DOWN into the car over the studs. There is not enough room to push the fan into the studs.
*Then take a jig saw and cut the top of the fan shroud right where the fan opening is (hard to explain w/o a pic) Trim about 1" off then break off the skinny "finger protectors" so basically the top 1/3 of the fan is exposed with nothing BEHIND it, but the edge of fan itself is still inside the fan shroud. Hard to explain but you'll see when you try to reassemble the air box, just look at what it's hitting then cut it off.
Worked for me, can't even tell the radiator was replaced. BTW this was WITH the newer fan, not my original '97 fan.