http://www.blueridgediesel.com/P1010019.JPG maybee this link will help with tag that everyone is talking about

3CB1
Left Side, lower center of block between front engine mount and starter
3CD1

3YA1
Right side of block above injection pump.
3YC1

2KC1
Right front, on injection pump mounting flange.

3KC1

3KR1

2AB1
Right front, top part of the cylinder block.

3AB1

3LA1
Right front, top part of cylinder block. Between 1st injection pump and front cover.

3LB1

3LD1

3LD2

4LB1
4LC1
4LE1
4LE2
C240
Left front, top part of the cylinder block.

4JA1
Left rear, top part of cylinder block.

4JB1

4JC1

4JG1

4JG2

4BB1
Left front, top part of cylinder block.

4BC2

4BD1

4BG1
Left side, center of block between tappet cover and engine foot, or Left front, top part of cylinder block.

4BG1T

6BB1
Left front, lower part of the cylinder block.

6BD1

6BD1T

6BG1

6BG1T

6HK1
Right front, top part of cylinder block below number one exhaust port.
6SA1
Left rear, top part of the cylinder block.

6SA1T

6SD1
Left center, lower part of cylinder block.
6SD1T

E120
Right side of the cylinder block, below the injection pump and to the rear of the oil filter.

E120T

6RB1

6RB1T

6WG1
Left front, top part of the cylinder block in front of the injection pump.

NOTE: ALL SERIAL NUMBERS ARE STAMPED AND CONSIST OF SIX (6) NUMERICAL DIGITS. All directions are as viewed from the flywheel end of the engine. The Engine Model is cast on the side of the block or located on the ID tag, which is found on the valve cover.