The 5.9V8 pistons withe the oval soap dish increase “tumble” ( or barrel motion )

The original flat top 5.2 pistons probably had superior squish jet effect.

Original 5.2 pistons seemed to be slightly less than 20 thousandths in the hole

5.9 pistons seem to be slightly more than 50 thousandths in the hole.

The 5.9 needed a custom cylinder head design.