previos owner says he did the swap from l99 to ls3? but how can i tell from a visual inspection??? thanks for any help.

 

I am mostly ignorant to the newer Camaro's, but it looks from brief reading that the L99 came with automatics, where the LS3 came with manuals.

Camshaft Upgrade - Too Fine L99 - GM High-Tech Performance Magazine

I am not sure you can really call it a swap. Look at the differences listed in the article. To make it an LS3, there would have had to have been a cam swap, changes to the heads, and unknown changes to the computer to disable the AFM and VVT components.

If you still have contact, I would verify what was actually done.

 

I think he was taking about a cam swap and supporting valve train to get rid of the VVT and AFM which needs a tune to to get rid of them.

In the 5th Gen world listed above is a "LS3 swap."

 

L99 and LS3 are the exact same on the outside EXCEPT for the timing chain cover.
L99 has a phaser cam location and the LS3 does not.

If you have a regular timing cover as pictured on the right it could be a LS3 or a L99 with a cam swap basicly.

 

The ONLY way to know is to take off a head and see if the pistons have Valve reliefs for VVT.