The CP3K is a pump that will flow the same as stock volume, but has flow modifications to allow it to fully fuel over 3000 rpm. Stock CP3's have a flow restriction built in from Bosch that starts to throttle the fuel flow back at 3000 rpm. Fleece modifies the CP3K to no loger have that throttling device. The pump is rated at 600hp and allows full flow after 3000 rpm. (A great option for a dual pump setup as well!)
The PowerFlo 750 has the same 3000 rpm flow modifications as a CP3K, plus it has a larger stroke cam (10mm) that will allow it to flow enough volume to conservatively support 750 RWHP (with the right supporting modifications).