Few questions about replacing PS pump

[01smoker]

I am having to replace the ps pump on my 07. It has the intermittant problem where the steering just wont move. Does it more often when the truck is cold and I need to cut the wheels sharply. Then all of a sudden it will just start working fine. Flushed the fluid once and it helped for a while but now its back and getting worse.

Anyway, Im looking at the O'Reilly website and it lists 4 different pumps. Which one do I need? With or without reservoir and with or without ZF pump? Or should I just go to the stealership and get the upgraded setup for an 08-up truck?

Thanks in advance

 

[Crysis]

I bought a pump from O'reillys and it burnt up in less than 1 hour of driving time. The seal on the front is what burnt, and the shaft looked like it had been heated up. Went and bought one from Advanced Auto Parts and it hasn't gave me a problem yet. The one from O'reillys was just the pump itself. The one from Advanced was the pump with the reservoir.