I just bought a '09 Sierra 5.3 . Engine is toast. Will a 5.3 out of a 07 sierra fit perfectly? The 8th digit of the 09 VIN is "J" 8th digit of the 07 is "0"

Call a salvage yard and they can tell you.

I wouldn't trust them for that kind of info. They may not be able to distinguish fueling systems.

The interchange books will tell, but then again, they have to actually read it.

Are you in California (or other area that follows California'* rules)?

If so, it'* illegal to change your engine out for one that is any previous model year, even if it is otherwise the exact same thing. Unless it is an off-highway vehicle, and even then it is iffy.

2007 was a weird transition year for pickup production. I wouldn't go to a 2007 engine, especially with their propensity for AFM-related oil-consumption issues.

That was the other issue I couldn't remember. That stupid AFM crap.

Yeah, it got better in later years, but 2007 was the first year. I have a friend that has a 2007 5.3 . . . I call it a "two stroke" because it takes a quart of oil every 500 miles or so.