I picked up what I think is a '73 455. The casting number is 1241735, which would be correct for late '72-'75 blocks, it has the "73 cast on the exhuast flanges on the heads, but it's got a production code of "CF" stamped on the block. I've never seen this code and I can't find it in any documentation. Would have expected an XF or XS code for '73. Any idea what this is? Thanks, Donny
