94ls

What is the numbers on the cylinder to identify if it's a 5.3 or 4.8 I have three different numbers 706 1706. 1256

76larkman

You need to look on the block. Heads wont tell you that. Front of block right of water pump is a casting saying 4.8, 5.3 or both. May have to remove steering/ altenator bracket to see it. Other is on back of block behind flywheel on top.

94ls

But if it has both how can I tell which one is right

76larkman

Being together you cant measure its stroke. 4.8 and 5.3 same block and bore size. Most 5.3s have dished pistons but L33 5.3 "B" code engines are flat top pistons. All aluminum as well(block). Take a spark plug out turn engine over to can see piston top looking thru hole. You can use a wire or screwdriver thru hole and feel piston top. Outer piston top edge will be dish piston if feel slight rise. If not its probably the 4.8. Nothing wrong with a 4.8 engine tho.

94ls

The block is not aluminum it has 5.3 and 4.8 on block so I'm thinking it's 5.3 cause the top of piston is like a dish plate thanks for all the help