What is the difference between an '01 and say and '04 lift pump for the 5.9 engine?

Were they improved? Totally redesigned? Or do they have the same problems?
Just curious.

 

Simply put, not redesigned - totally different pump, similar problems. Realistically, they aren't much better. The failure rate on the 03-04 filter mounted pumps was high. The in tank pump has proven to be considerably more reliable, though, mine died on me.