I bought a new, unopened Delco water pump last month, #12482919/GM #251-545 (stamped # on the actual pump housing is 12564115) and the blades look similar to those on the pump on the left.
Did someone rip me off?

I like the machined gasket surface on the right one. I'd buy one just for that, then I'd set it on my desk at work and admire it all day. ...where'* my wallet?...

It would seem AC Delco went through a re-design.

This is the OEM water pump that just came off the Zilla:

Wow, go figure! Thanks for posting!

New one looks like a definite improvement. I just installed one of the stamped ones a couple months back
I remember years ago (in 96?) I had trouble finding one. Some of the aftermarket ones that NAPA was selling back then had the impellers mounted on the shaft crooked and were rubbing the casing. I had to open several boxes before I found a good one.

Willwren

Does the pump on the right have a solid cast iron impeller?

On my old 1970 cutlass swapping from a stamped to a cast impeller dropped idle temp a solid 5*.

It is solid cast. And the measured/roughly calculated surface area of the impeller blades is quite a bit more. This pump will flow about 15-20% more than the Chinese pump pictured at the beginning of this topic, and the old OEM that I removed last night.

So your 10% underdrive pulley will now flow to ~5 to 10% above normal?

Not basing this on angle, nor have I accurately measured the diameter. Hard to say until I get to a more quantitative analytical anal retentive analysis.

If I order it from GMPD, do you think it would be cast or stamped?