No casting numbers on the shelf on the pass side?

[trevor73402]

Hey all,
I was working on my $300 suburban today and decided I'd check the casting numbers on the block since I had the alternator pulled off. I scrapped all the grime off and there they were. It was a Flint plant 350. Well my 84 K10 was sold to me claiming to have a rebuilt 350 in it. I've always been curious if it really was or if they previous owner just told me that and hoped I wouldn't check. Well I got a flashlight and a rag and wiped the shelf off, but its blank? No numbers on it. It's just shiny and smooth. I'm looking on the little shelf just behind and below the alternator. Any suggestions?