Ford 2006 F-250 Owner's Manual page 302

Maintenance and Specifications
1. World manufacturer identifier
2. Brake type and gross vehicle
weight rating (GVWR)
3. Vehicle line, series, body type
4. Engine type
5. Check digit
6. Model year
7. Assembly plant
8. Production sequence number
Engine number
The engine number (the last eight numbers of the vehicle identification
number) is stamped on the engine block, transmission, frame and
transfer case (if equipped).
TRANSMISSION/TRANSAXLE CODE DESIGNATIONS
You can find a transmission/transaxle code on the vehicle Safety
Compliance Certification Label. The following table tells you which
transmission or transaxle each code represents.
302
2006 F-250/350/450/550 (f23)
Owners Guide (post-2002-fmt)
USA (fus)