318 pistons
Rusty is right, I did a lot of research on 1968/69 318 engines. I checked several stock engines by my self and can confirm that you can find both pistons in them. Even the book on how to rebuild a small block is wrong on this subject. They put in there whatever was available. More important is to check the standard size of the pistons and bearings.
Here pictures of stock factory 68 318:
Rusty is right, I did a lot of research on 1968/69 318 engines. I checked several stock engines by my self and can confirm that you can find both pistons in them. Even the book on how to rebuild a small block is wrong on this subject. They put in there whatever was available. More important is to check the standard size of the pistons and bearings.
Here pictures of stock factory 68 318: