Originally Posted by tclederman
The block (and the head) casting codes (and, date dating codes for head and block) would help to distinguish a 216 from a 235.
try bouncing the casting numbers as Tim suggest

http://www.inliners.org/casting/numbers.html

here is the link he gave you earlier
http://www.1954advance-design.com/Web%20images/casting-code-photos/low-press-codes-ser-nums.html