JDM engine swap

3.4 -> 3.4, you're fine in CA.

Issue comes when you try and do 3.4 -> LSX or an engine that wasn't originally in the truck from the factory.

I see complete engines (minus accessories) on Craigslist in Los Angeles for $999-$1100 all day long with warranties.

 

The test they have trouble getting past is called a "shake" test if I remember correctly. Too expensive to make the vehicles compliant.
I bought one of these JDM's in 2014 and paid a guy I know $600 to drop it in for me. He had to swap out some parts from my old engine to get the configuration right but he didn't seem to have an issue with it. I've had fantastic luck with mine, I've talked about 85,000 more of my truck sets and have not had one single issue with it. All together I got the new motor and got it installed for just a little over $2,000.

 

I had 111K on mine and I put a rod right through the block. From what I read if they're going to fail early that's how they would fail. I think a contributing factor may have been when I change the thermostat a year or so earlier I forgot to burp it and got it hot. All seemed fine and I put many miles on it afterwards but there's no way I could tell if that was the reason or not.