1970 hemi block id

[Dan Brooks]

I have an opportunity to buy a hemi block and cant find out much about it, here are the numbers,
block casting- 3577430-1
date- 1-19-70
I know this is not a production block and have gotten numerous different emails as to what it is but would like to hear it from you in detail, thanks.

[scottm]

I understand it's called the D5 block, a heavier version of the 426 HEMI, cast for Pro Stock racing.