Great. Thanks for the help. The casting number could easily be 568557. I looked again last night and I am still not sure...

The car did come with some extra parts including another set of heads. The heads look to be 13 with a date of F259. So if I looked it up right they are 72 CC heads which should be a lot better than the 96 CC heads. So my next question is are the 13's good heads?

Here is a pic of the old bird in case you are interested. Firebird pic