There's a machined pad on the block, just ahead of the passenger-side cylinder head. There should be a number stamped on it, followed by a 2 or 3 letter code. The letters will tell the story, displacement, and year of manufacture, and usually what vehicle the engine originally came in. A diamond shape on top of a rectangle on the ends of the heads denotes a 58-CC high-compression head with relatively small valves, used on high-performance 265 engines in 56 and 57, and 283 engines from 57 through about 1965. With bigger valves, 1.94" intakes, and 1.6" exhausts, they will breathe pretty well, and make 11:1 compression on a 350 with flat-top pistons. I do that on "claimer" engines at the race track pretty often.
Jerry
