Prospective purchase engine ID help, please!

[sixbrl440]

Looking at a 1967 Corvette, which I know has had the 427 changed for what is in it now. The present owner has had it almost 30 years, not too knowledgeable about the numbers of the car, just bought it back in the day for his son. Long story.

Anyhow, it is 3999289 cast block, I couldn't read the other stuff as it is in the car, with this on the pad: CE 103507

I figured out it is a 454 block, but what do the pad numbers signify? FWIW, I am a MOPAR guy, so this is kinda Greek to me.

I am told the bore of the block is the same as the original 390 HP 437 would have been [4.250] and the engine has the original heads and dist. Weiland manifold has been installed, along with a Holley 750 carb.

Any help would be appreciated.