New LS1 Owners - Newbie Tech - head identification help

I pulled these heads off a ls4 5.3. I had a couple of ?'s 1 I read that these are the same as the heads on an ls6, is that correct? 2 can anyone tell me if these are the correct heads or any information. Under the valve covers are numbers two sets of four after the GM stamp first set 1256 second set 1706. On the corner there is a number outside the valve cover 706. Thank you.

you want 243 or 799 castings.

you want 243 or 799 castings.

Not sure what that means. I'm fairly new at this and learning as I go.

What is the 3 nummbers on the upper side of the heads?

There is the number 706 on the top of the heads.

706 are 99 to 04 gm 4.8-5.3 motor. 243 heads are what a ls6 has.

Thank you.

Is there a place I can find this information? I also need help identifying a block.

Yes the magical google search.....

http://lmgtfy.com/?q=706+head+casting+specs