Try the frequently asked questions section of
http://www.442.com Has loads of Olds info on engines, heads codes where to look.
Engine ID on an Olds 455 (and I believe all Olds in this vintage) is on a pad, by cylinder #1, which may be blocked by power steering or alternator brackets.
Check out the FAQ section, it will help ID almost everyting, heads, carb, dizzy, exhaust manifolds etc
John