Anyone have blue book info for commercial trucks?

I sold mine and am going to the bank Thursday to buy this one. I am curious what blue book loan valve is on a:

2003 T-800 KW,390,000 miles,c-15 475 Cat engine,13 speed,nice condition inside/out.All options except Jakes.Daycab-dual tanks.

I don't think trucks have blue book. They have a black book but it cost money to get the information. There was a thread on here a while back about it. That's all I remember.