i had a Hydor L35 in my setup with a DD TDX block, DD bay res, and DD black ice extreme single 120mm radiator, all with 1/2" fittings and tubing 1/2" ID - 3/4" OD, and it really screamed the water through there
cheapest deal i have found on it, in case you are shopping is at MarineDepot, also make sure to pick up a Criticool Powerplant II PCI slot relay card to wire it into, makes bleeding and filling nearly painless, makes the pump cut on and off with your PC so no worries if someone else turns on your PC and forgets to turn on the pump