I was going to say that but I was not sure everyone thinks of it like I do. These things are two up and two down with lots of bearing surface. They are not extremely balance sensitive and will shake no matter what. Not as smooth as a six.I swapped in another set of 307 SBC pistons just to check deck height. Balance was fine with pistons and pins out of the box.

"I wonder if God created man because he was disappointed in the monkey?" Mark Twain