Fuel pump regulator

I have read several posts about fuel pumps and engine swaps but a few things are still in the grey area. I am almost finished with my 98 4.0 into my 89 using the 98 head and 94 intake with renix computer but i have ran into another problem. I tried adapting the fuel pressure regulator off of the old fuel rail to the new style fuel rail with a little cutting and welding but i keep getting leaks although it looks good. So i decided i will just get another tank and pump with the regulator built in. So i looked up part numbers on the auto zone website says that 91 fuel pump is the same as 89. This doesnt make sense because 91 fuel rail didnt have a regulator on them. If someone could help me out it would be greatly appeciated.

They didn't change to the in-tank regulator until the switch to the OBDII ECU in 96. That is what you want yours from but remember that these run the pressure at 49 psi instead of 39 psi for the 95. You should really run the later model injectors with it as well.

why couldnt i use a fuel rail from a 91 ho did they have the pressure regulator on the fuel rail? Will the fuel rail bolt onto my 94 intake?

The fuel rail for the 91 will bolt right up. I would suggest also getting the hardlines from a donor jeep though because the hard lines are different. And yes it has the pressure regulator on it. I swapped a 96 ho into my 89 and that's how I did it.

Yep they are fully interchangeable as I have a 95 rail fitted to a 01 inlet manifold.

Thanks guys just fired it up ran good. A few more odds and ends and i will be done.