Newbie needs help decoding!

Thanks for the reply. Is that the way most A-body enthusiasts look at it?
I realize V-8s are worth more, as a rule, but have always respected /6s.
I am a nut about originality and wondered if I had missed something here. Perhaps the block was replaced with a 65 and was stamped or re-stamped to look like a 64?
Or the factory sometimes pulled newer blocks intended for the next year?

The collectors, in general, are looking for the rare/desirable variants - /6 was the grocery getter econo-model.

I'm having fun with a /6 in my '64 GT, but I'm doing a stroker small block in my '64 wagon.
Neither will ever be worth what an unusual optioned/big motor/later car would sell for, but I'm scratching my own itch.