Can you remove the 16" fan from it's cage and mount it in a custom shroud. This is what I did, and it shrunk the room needed quite a bit. My shroud is slightly deeper at the top than the bottom. I ended up using a 14" and a 10" fan in my custom shroud. My shroud is 1.125" deep on top and .750" deep on the bottom and the fans are mounted inside the shroud. This puts them pretty close to the radiator. My car has an all aluminum blown 406. I have not had any overheating problems even when the temps are in the 100 degree range in traffic, 190 degrees all day long. I to am running a Walker radiator. I know I didn't answer your question directly, just wanted to let you know there are options. I don't particularly like pusher fans, they can cause flow problems through the radiator at cruise speeds.
Keith