Exhaust differences in 2000 XJ

Swapping engines this weekend and would like to know the difference between the donee (two pre-cats on header) and the donor no cats. I have both complete XJs. Do I swap headers or can I use the one without the pre-cats and change the computer? I'm not even sure the pre-cats are original. The engine has been swapped once before I owned it. Both are 2000 models.

The precats are in the down pipe, part of the exhaust system. The manifolds are the same, but the non cali emissions has the two O2 sensor ports in the manifold plugged with bolts.

Thanks Talyn. I see that now. Donor engine is out and sitting on the garage floor.