A friend just bought a 1966 closed chamber SQ port head it has the casting # under the valve cover, but everything else is different. It doesnt have a date on it, it also does not say HI-PERF in the center of the head under valve cover, It says HIPERF in small letters on one of the runners next to casting#, in the center where most say HI-PERF it has 2 different series of numbers one starts with O- followed by 5-6 numbers other is short with 3 numbers/letters. I wrote everything down and where it was located, but I left the peice of paper at work. Has anyone seen an #858 like this ?????????