How rare are 273 Commando factory pistons .030 over ?

Kemper said
I don't think those are the L2222N that Chrysler used in production.

Yes, that's them. You really should familiarize yourself with what you're talking about. Here they are from Egge all the way from standard size to .060. You have some very experienced people trying to help you here. You should listen.

https://egge.com/product/egge-piston-set-with-pins-177/