The fan in an AD/ late-model swap (552nd on, 235, 261, 250 or small block) will not clear the lower radiator outlet if the radiator is in stock position. With a pair of heavy-duty tin snips you can modify the radiator mounting flanges to drop the radiator about four inches or so. You'll need to drill new bolt holes. Then a 16" fan will clear the outlet. Using a shroud with such a setup will require some good sheet metal skills as the fan swings lower than the radiator's bottom tank. It clears the cross member, though. I've done this using a 6-blade, high-pitch truck fan and a 4" radiator core. I put an electric pusher in front of the radiator but it only comes on after shut-off on a hot day. Oh, one more thing: I moved the radiator to the front side of the mounting hoop, though there are work-arounds these days I understand so you don't have to do that.
