1965 273 Heads

Okay.... I'm convinced - heads are heads (at least in this instance).

Laysons has 273 Commando pistons - as factory replacements, and also in 30 over and 40 over - but Layson's is VERY overpriced (with all their parts, typically).

And I had wondered about the octane business, too. With such high compression in the Commando engine, you'd probably be faced with adding octane boosters each time you filled up.

Anyway, I'm really not looking to build a racer............. but someday, an upgrade to a 340 would be cool.