How to tell the model?

[Crutches]

I just bought an O5 3500 crew cab 4x4 6.6 liter. How do I tell if I have a lb7 or lly? Is there a page to explain the model letters? Yep, I am new at this.

[Kennedy]

I could tell you without looking, but better for you to to learn. I have it broken down here:

http://www.kennedydiesel.com/categoryresults.cfm?Category=4