Originally Posted by jforse
So. Since I have the early pump in my fuel cell. Should I buy a later TJ pump or do a different aftermarket pump?
I've heard of people running both with a 5.3 and it working fine. I forget the numbers off the top of my head and I'm on my phone or I would search but iirc the early pump is rated roughly 5psi below the later model pump. It's on the low side of the recommended pressure for LS engines. I've also heard of some having minor issues of fuel starvation with old, tired pumps.
Since you have the RCI with rings for the factory pumps it would probably be easiest to run the late model factory pump rather than modify the cell for another top plate. If you were to switch I would consider assembling a in-tank system with center pickup with either a Walbro or Bosch pump very similar to what Wayne at Alltech builds and an external reg and filter. His drop in dual pump setups for Ultra4s are a bit pricey but I'm going to piece together my own system and try to save a little. I'll do a write up in my thread when I get to working on that.