I think I would spend an extra few dollars on making sure
the entire engine has been balanced by a shop that specializes in
this. It'll add another 400 or 500 (U.S.) to the price, but will
really make a difference in smoothness and longevity.

When I was researching my options with our Lycoming O-540, I was told that
balancing a normally aspirated air-cooled engine is a waste of money. The
imbalances in fuel distribution are so great that any improvement in
smoothness the balancing might impart would be obliterated by the normal
"roughness" (relatively speaking) of the engine.

A fuel-injected engine is a different story.

I went with all new Millennium cylinders, and a field overhaul at a trusted
shop. We've been very happy with the results.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"