[05_LLY]

You can tell by the 8th digit of the vin these are the vin numbers with there engine code,

8th Vin #1-LB7 300 hp
8th Vin #2-04.5-05 LLY 310hp autos only, 300 hp manual trans and 4500/5500
8th Vin #3-06 LLY ratings are the same as vin 2
8th vin #D-LBZ 360 hp auto only, not an option in manual trans or 4500/5500 trucks

 

[05_LLY]

No Problem!!

 

[05_LLY]

No i think it has more to do with production.
GM seems to do all there changes half year instead of new model year for some strange reason??

Ford dosent really do it but dodge dose they just use cool terms like high output for the bigger hp version!!!