Head gasket compatibility help

[gapost]

I am working on my 03 Sierra 4.8l and I was getting ready to install the re-built heads. BUT, I looked at the old head gaskets and the number on them is 12558940. From everything I can find, these gaskets are for the 1999-01 models. I have a Felpro head gasket for the 03 4.8l, number 26191PT, that says it replaces 12575329.

 

Needless to say, I am a little confused and wonder if my engine is not the original. The only thing I see different on the gaskets is that the new ones have an opening for a coolant hole at the back of the block that is not on my block. The old gasket had that hole opening solid (no hole). My heads are 706 heads and do have that hole in the heads, but of course, not in the block.

 

So my main question is, can I use what I have or do Ii need to do some more checking. My casting number on my block is 12551358, which means it is basically a 99-03 block.

[XYZ]

First thing I would ask you is, have those 706 heads been checked to make sure they are not the ones with the porosity issues?

[XYZ]

I just had to swap the heads on my 2003 Sierra with the 4.8 due to this.....

2008-12-05_142924_Coolant_loss_5.3.pdf

2008-12-05_142924_Coolant_loss_5.3.pdf

2008-12-05_142924_Coolant_loss_5.3.pdf

2008-12-05_142924_Coolant_loss_5.3.pdf

[gapost]

Yes, I know about those heads. I have replaced several but these just came back from the shop and they tested them.

 

I'm just going to put the heads on with the gaskets I have and hope it works okay.