[blykins]

Got your email, yes it's a C5AE-F head. Factory 427 medium riser.

Now, for the kicker....

I won't be able to tell you exactly what you need until those come off. In factory form, the chamber sizes were supposed to have been 88-91cc. That means that only a Pond aluminum head would be a good substitute, in order to keep your compression ratio down.

However....

The last 427 I built for Alan Carter, a forum member here, used those heads. After cleaning the decks up and a valve swap, they were at 73cc.

You can never tell what's been done to a block, or to a pair of heads in the last 50 years. They may have been milled to death or they may be factory fresh.

I think if you're ready to do a swap, I would suggest mothballing the car for the winter, then have your shop pull the heads and cc the chambers. That way, we can approach this as a methodical engine builder instead of throwing parts at it.