Hi, I have a few supposed S5 13B's lined up to buy, and I was wondering if there are any ID casting numbers to differentiate the S5 from the earlier 13B's?

 

Not that I've ever heard of or seen, but you can tell an S5 engine from S3 (GSL-SE) or S4 easily from the front cover. If the metering oil pump (MOP) is electric, it's an S5. There are other differences, but that's the most obvious.