The three (3) slides for installing the hard drive cages in can be taken out by removing two (2) screws each.
Removing the hard drive cage slides allows for a 240mm radiator to be installed in the ceiling of the PSU chamber. There is enough room to have the ports on either end, though you may not be able to use a fan on the back, depending on configuration and fittings.
There is also room for mounting a 280mm radiator on the PSU side, but you will have to be selective about what radiator you go with. Pictured here is a Hardware Labs GTX 280.
The Hardware Labs GTX 280 is a little bit wider (~9mm) than many other brands, but it does still fit inside… but only just.
This is why we don’t like holes drilled, and greatly prefer having slots for mounting fans/radiators. The fan screw hole spacing is 15mm, but not all radiators (such as the Hardware Labs 280) have 15mm hole spacing. This means if your 280mm radiator doesn’t have 15mm spacing, you’re stuck using just the four (4) screws from one (1) fan to hold the radiator up. There’s also no flexibility with the 280mm radiators to mount the fittings anywhere other than the front. Again, slots would be better here. The maximum size Fractal Design states for here is 325mm long, 140mm wide, and 130mm thick.
Taking a look at the motherboard chamber, there is also room for mounting a 240mm radiator on that side as well. These fan holes are closer to the side panel, so the Hardware Labs GTS 240 pictured will not fit. With the GTS 240 being ~4.5mm wider than something like an Alphacool 240mm radiator, the GTS hits the window in the side panel. An extra 1/4” would have been nice to accommodate more radiators. With the motherboard installed, there isn’t room for a 280mm radiator on this side. Fractal states that the maximum radiator dimensions for this area are 280mm long, 120mm wide, and up to 60mm thick (including fans). Just keep an eye on your RAM clearance.