picked up a 350 chevy 4 bolt block 3970010,cast and assebled in 1975, was reading up on chevy small blocks, it said the samll blocks with high nickel content had a 10 or a 20 cast into the block under the timing chain cover, on my block there is a 020 cast into it but there is 4 or 5 other numbers cast right above it, just wanted to know if it was a high nickel content block or not, i read they stopped doing that after 1973, but that was in a small block mopar book.

thanks
Russ