6.9 factory upgrades

[k828]

What, if any, factory upgrades were done between '85 + '87 to these engines? I have one of each and want to know if one is any better than the other to put in my project truck. Thanks. Ty.

[cdnsarguy]

The 85 year was the block change period due to the Block Heater frost plug hole cracking on earlier years.....

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