Fan upgrade question

Most important is a shroud that fits close to the fan. I think a factory clutch/fan is best since it has many big blades that move a lot of air at low speed, without robbing power on the highway. If you add an electric pusher fan on the front, I have read that several factory fans are much better than after-market ones. Many use a M-B fan or a Ford 2-speed. Read up on rodder sites like HAMB.