5.3 with 799's, need higher compression
 

If I am not mistaken, my 2007 5.3 has flat top pistons, I already know it has 799 heads. I am deleting the DOD ad I plan on running a cam with a pretty long overlap, which will reduce the static compression. Is there another LS head that has a smaller combustion chamber that will bump the CR?

The only other stock ls head with a smaller combustion chamber that I am aware of is the 706/862 castings put on the 4.8 and 5.3 motors of the earlier years. There is no point in doing this swap though as you will get a bump in compression but will lose on the flow side. The 799's have the same flow numbers as a 243 casting I believe which is:

64.45cc combustion chamber
210cc intake port
75 cc exhaust port
@.600:
intake = 257
exhaust = 183

The 706/862 casting I refered to has:

61.15cc combustion chamber
200cc intake port
70cc exhaust port
@.600:
intake = 226
exhaust = 174

So in short your gaining compression but loosing flow. Your best bet would be to have your 799s milled or to buy an aftermarket set with smaller combustion chambers IMO.

^exactly. Take .020" off the 799s and you should drop about 3cc, giving you roughly the same CC size but in a better flowing head.

just mill your 799s to 59cc and get alittle higher comp imo

yes mill'em. the norm is .030" and that would put you in the 60cc range. do a .035" would get a 59cc. not sure on the comp ratio, but guessing over 10. could go with a .041" cometic gasket for a little more. i milled my 862's .050" for a 55cc chamber. you also need to factor in the new 5.3's have valve reliefs cut in the pistons.