Actually I took part in another thread here on the forum. I got answers who confirmed the information I've got earlier, but wasn't sure was correct:

1. All CSB earlier then the LS1 have the same direction on the cooling water.
2. Serpentine belt systems have waterpumps who runs in the opposite direction because the pumps are located on the outside of the belt. BUT those water pumps nevertheless pump the cooling water in the same direction as the older pumps, because they are a kind of mirror-like.
3. The only thing to remember then is the cooling fan, which of course must be changed.

But thank you for the information on the heads anyway.
I haven't decided any change of heads or cams yet. That will be a next step after the hot rod have been on the road for a while.