Aluminum C-Channels and plexiglass anyone?
Basically, cut out the plexi to install both fans, drill all the holes, ect. Then measure how big the radiator is. Then, measure out the C-Channels and cut them to form the outside ring. Then cut the plexi to fit the inside of the C-channels and glue it in there and glue all the C-channels together. You can thread bolts through the radiator fins to secure it.