I purchased them though a company here in Australia called Hemi Performance. They are from a 318 truck motor apparently, but the 273/318 heads are exactly the same so will bolt up without issue. If you zoom in on the photo I posted you can see the cast number but I have researched those numbers and they aren’t listed anywhere. All good, I’m happy with the purchase!! I had them delivered for $700aud for the pair. With the exchange rate from aud to usd you would get them a lot cheaper, probably enough to cover the freight.