Engine install on assembly line

rwh1966 said
It’s a 2465330 I’ve looked inside it has dome pictons , the intake has the early bolt pattern

So it's a 65. Or the heads are anyway. Was it a left over from 65 into your 66? Anything is possible but probably not. What's the build date on your car. It would have to be a early August build to receive a leftover 65 engine.