457 listed on the end of the heads. Tom at Champion says they were made June of 99. These ran fine on my car but the guides leaked oil, so I removed them. They have been cleaned and have two cracks. One is under the logo and the other on a outer bolt hole. Tom says that it would take about $500 to make these right. I am including intake and exhaust valves, 1.55 Scorpion roller rockers, rocker studs, push rod guide plates, and polylocks. I can see no other previous repairs. $800 + shipping