Posting for an acquaintance:
"Anyone one know if there is actually a difference between the low emissions and the standard emissions long blocks?

BP4W-02-300A (Federal)
BP4Y-02-300A (California)

My car is actually a California car, but federal engines are obviously easier to find. I thought the only difference was exhaust and ecu. "

 

The only things I'm aware of are the ecu, exhaust manifold (pre cat), midpipe (no post cat o2 sensor bung), underhood wiring harness (change in o2 sensor location), dipstick and dipstick tube (to clear the precat)

Internals should be the same AFAIK.