Hey guys. I am looking into getting a Celsior for my dad since it is a awesome luxury vehicle. Just wondering how to know which options are included? I am looking towards either the 1999 body style or maybe the 2000 body style. I know they have different types of engine as I can see one is 4.3L and one is 4.0L. My main concern is the differences between UCF30 and 31 and the differences between UFC20 and 21. What options change between the different available packages? (C use, CF, B use)? I have heard that these cars came with rear massaging seats and power reclining rear seats, any way to tell if certain models have these options? Any info would be great. Thank in advance!