440 pad

I come across this. What's it mean?

There's good info HERE on block stampings and casting #s.

Also appears that some shop that goes by SSRE did some work on it at some point...

I bought a 426W block once that said MATT LENT on the pad. I asked the guy what that stamping was. He said, oh, that is my name.

SSRE:
SS Racing Engines?
Super Stock Racing Engines?
Might be worth a Google search as it appears they numbered it and may be able to tell you something about it.

This guy ?
https://www.shafiroff.com/

Scott Shafiroff?
Steve Schmidt?
Stanley Steamer?

I once had a set of TA heads marked “Petty Enterprises shrt trk “. I got screwed out of them by a friend. They were good flowing heads.

In case you didn't know...that's a '67 HP 440 block assembled August 25th out of a '67 car. Not sure if you were only asking about the "SSRE" part or not.
The "SSRE" is just some shop that did work on it sometime in the past.