Not sure how to break the news but - new t'stats and water pumps rarely solve overheating problems - unless the t'stat was stuck closed.
Water pump failure is almost always related to seals leaking. Even stock pumps have enough excess capacity that as the impeller becomes coated with deposits, they still usually pump just fine. And lowering operating temps with a new t'stat simply buys you a little time -- it usually takes a little longer for the system to heat back into the overheating range, that's all.
Dumb questions first - you sure you put the t'stat in facing the right way? Spring towards the engine?
If you're overheating, it's likely because either the radiator is no longer capable of rejecting enough heat, or the fans aren't moving enough air across the radiator at low speed. Underdrives can contribute as both the water pump and the mechanical fan are turning at lower speed which sometimes combines to cause problems -- not moving enough coolant quickly enough, and not moving enough air across with the slower turning fan.
So, tell us all about your radiator and your fan set up.