455 olds heads verification. who can verify numbers

[kcsteck]

Im lookn at some heads supposedly the sought after 68-69 455 C casting. can someone tell me if these are legit or not? 394 and 548 marked on them on top and a little 10. let me know.
Casey

[Mark Sims]

the heads have a letter designation B,C,D,E,F,G, etc. any head can be made to flow fairly well. avoid J heads if possible. small block heads use numbers 4,5,6,7,etc.