I have a 69 383, so it should have this pump housing. I'm out of town for a few days but can get a casting number for you on Tuesday. It is on a running 383.
If you haven't made a deal otherwise, I got the numbers on my water pump housing. It is 2870987-6, the date code is 3X03 (no idea what that is), and it has the pentastar on the outlet (driver side). Photos are below. I'm asking $50 plus the ride. I'm guessing this will fit in a medium USPS flat rate box, so shipping would be $15. If you want the water pump too, add another $10 and as long as it all fits in the box, same price for shipping.
This came to me on a running 383 for which I got video of it in operation, from a trusted member of the forum. Shoot me a PM if you are interested.