Did it run hot like this in traffic before you swapped the radiator? Did you ever put the correct radiator cap on it? Verify that the electric fan you have is spinning the correct way when on.

A lot of cheap fans spin well when there is no "load" on them, but fail misirably when they have to pull air through any type of restictive set-up. You do have what looks like a well-made, tightly sealed shroud. Either switch to a good factory type electric fan (there's a guy on this site that sells a nice big GM fan with shroud), or get yourself a high flow 16" Spahl fan or the dual 12 inch Spahl fan/shroud set-up with the good Spahl controller. (It will suck the chrome of a trailer hitch.); OR fit the factory stock/style thermal fan and shroud back on it. They move massive amounts of air too.