340 .30 over pistons and rings
They are silv-o-lite 1267 .030 over.
I purchased a 68 gts motor to build up for my 68. The person I bought the motor from had had it rebuilt but complained that the motor had excessive blow by. I checked things out and found that the builder put standard rings on the .030 over pistons. I bought new rings and was going to use aluminum heads to get my CR round 10:1. I decided to use a set of x heads instead and I did not want to cut the heads down so I went with a different set of pistons to get my CR up. This is why the pistons are basically new and the rings are new.