I am sorry to ask again, but what numbers denote an LS6 block?

 

TTT

 

definition?

Not sure what you are asking, but LS6 blocks come in the 02' and up f-bodies (maybe 01) and the 01' and up corvettes.

 

Awhile back a picture was posted where you could tell the external differences... the easiest way to tell is to look under the throttle body on the top of the block, look for the quarter sized "pedestal", and if its flat and dosen't look like a bullseye, its a LS6 block.

 

Well, that rules out my motor then, mine looks just like a bullseye. I have 2001 SS.

 

...in a LS1 block there is a hump under the valley cover which is not present in the LS6 blocks..

see the JMX instructions for installing an LS6 valley cover in an LS1 block...