I don't know about the number you found, but here are some pictures of the engineering number and date codes on my 88' block.
The engineering number is on the lower side of the block, driver side, by the bell housing.

The date code is in the lifter valley.

1989 Firebird L03
1993 Thunderbird 5.0 HO
1995 F150
Gonna be building a 351 Boss this summer!
Summer's over, never got to it...
This is my current build though
http://www.302w.com/Forums/forums/thread/1100.aspx