. If someone purchases a new engine (crate motor), they must stamp to serial number of the original engine on the new block. (But they rarely do.) . .Look for the casting number for positive identification. The USA numbers are different that those made for other countries tho the block looks identical. Numbers are on Right side of Chevys blocks and left side of GMCs. Look at web page for your number. <
http://home.znet.com/c1937/Cast.htm>.
. When you find the casting date, it appears like there's a plate held on with two screws. This tells whether it was made by the day shift, swing shift or graveyard, One round head screw and one flat head screw = swing shift. .
.Lou .