not sure if this will help,

"INTERNATIONAL HARVESTER DIESEL ENGINES
6.9L and 7.3L Core Identification

6.9L Old Style Block
Block Casting Number:


On left side of block (beneath oil cooler) 1805440C1
Note: Some 440 blocks are truly new style and must be visually inspected by raised donut around the block heater, frost plug (right rear). Old style below serial number 173828.
Visual Identification:
*No counter bored area for block heater
*No defined area on side of block for dip stick
*Thickness of cast iron around block heater 3/8" (.375")
Head Bolts:
*7/16, 12 point socket is used to torque head bolts
*Block tapped with 7/16-14 for head bolts

6.9L New Style Block
Block Casting Number: 1807996C1 Note: Some new style blocks have casting
number 440. Above serial number 173828.
Visual Identification:
*Has counterbored area for block heater
*Very defined relief area cast in side of block for dip stick tube.
*Thickness of cast iron around block heater 15/32" (.470")
*Latest style (not all new style 6.9) has ribs around head bolts, rear two on left side go from head gasket surface to pan rail - same as 7.3
Head Bolts:
*Same as old style 6.9

7.3L Block
Block Casting Number: 1809000 C1
Visual Identification: *Same as 6.9L new style block
*Head bolt ribs on side of block extend from pan rail to head gasket surface or rear two head bolts left side
Head Bolts:
*1/2" - 12 point socket is used to torque head bolts
*Block tapped with 1/2 - 13 for head bolts"