the last 3 codes you listed that were on the bottom of the sticker refer to your paint BC/CC is base coat/clear coat U 855 is the upper color code and 13D is the lower color code if I remember right

 

And, here's the Silverado details:

Silverado Decor/E63 XC - $0
Trim level: SILVERADO; Front power windows with one one-touch;
Partial cloth door panel trim carpet on lower door panel;
Deluxe sound insulation;
Leather covered steering wheel;
Seat back storage;
Driver and passenger power door mirrors;

Includes:
[C60] Air Conditioning
[AU3] Locks: Power Door
[ZQ3] Convenience Group: Tilt/Speed Control
[B30] Floor Covering: Carpet
[B32] Floor Mats, Front
[UM6] AM/FM ETR w/Cassette
[**D] Custom Cloth Seat Trim
[VB3] Bumper, Chromed: Rear Step
[VG3] Bumper, Chromed Front Deluxe
[V22] Appearance Package
[B85] Molding: Exterior, Bright/E63
[P06] Rally Wheel Trim;

Requires: [1SB] P.E.G. 1SB/Silverado Decor/E63 XC; Or
[1SC] P.E.G. 1SC/Silverado (Leather)/E63 XC

 

Still looking for the transmission model # - I got automatic, but not sure which. Anyone?

 

Check for it over internet.

 

MT1:Transmission: 4L80-E, 4-Speed Automatic, Electronic

MW3:Transmission: Manual 5 Speed, New Venture Gear

M30:Transmission: 4L60-E, 4-Speed Automatic, Electronic

M50:Transmission: Manual 5 Speed, New Venture Gear

MG5:Transmission: Manual 5 Speed, New Venture Gear



If yours is a auto it is most likely M30

Usually 1500 series M30 2500 MT1

 

You can get all the information on Google.com.

 

Or from GM if you have access.

 

I did get most of the info googling and ya'll have helped fill in most of the rest - that's what this forum is for, helping us all out.