Difference in crate engines

[Detroit Bill]

I was looking at Keith's crate engine offerings. There are two that are similar.

The lessor expensive 550hp iron block
428 FE 428-463 Street Crate

And the more expensive Pond block at 600 hp.
482/496 FE Pond Aluminum Street Crate

As best I can tell beyond the block the changes are displacement, larger valves and likely a different cam profile to go with it which results in more hp and torque.

Am I missing something there? I think the weight savings is in the 100 pound range for the block.

What is a "production block"? 390, 428?

Thanks in advance for your help.