I know this thread is old, but I'll throw in my 2 cents. I had an E2000 pump, and when I replaced my gas tank, I never could get the thing to prime again. I even sucked gas right up to the pump and it wouldn't go.
I forked out the cash for the Carter P5001 and it started instantly after I installed it. I don't think it's worth the risk to save $75. If you ever run out of gas or suck air on the trail, you could end up stranded.
If I ever get to go on a trail ride in the boonies again

, I'll seriously consider buying another for a spare in my kit.