Chevrolet: Motor I.D., chev motor, seven digit number

Question
Hello Jim,
I am trying to I.D. a chev motor that came in a Gasser that was raced in the 60's- 70's.
No number on the pad and the pad is very small compared to any i have seen. The block has a cast # on the bell flange drivers side :
57LG
S6I
Any info on this would be appreciated as we are restoring back to original.
Was told it is a 60's? corvette motor by the seller as far as he could recollect.
Regards,
Ken/ revshop

Answer
Ken,
   A common problem for some of the early smallblocks... When the deck was machined for work or racing after stock, a lot of folks didn't re-stamp the pad. There should be a seven digit number in the rear by to the left of the distributor that will be the casting number you are looking for, most vettes in the 60's started with 35, 36, or 37. The engine date code should be to the right of the distributor. If there are no factory casting marks in these spots, you could have an aftermarket motor or something like that.