Regular Production Option

While fairly complete, these do not include every RPO on a vehicle:

Beginning as early as 1967,^[6] and to all models since 1984, GM attached a Service Parts Identification (SPID) label. In alphanumeric order, it lists many of the options built into a vehicle, both RPOs and the older and longer Option Model numbers^{[7][unreliable source?]} sometimes used before 1970. These codes helped select correct replacement parts for warranty service. The label is most often located on the back of the glovebox door, on the inside of the trunk lid, or on the bottom of the spare tire cover. On some SUVs and mini-vans, the SPID label is located on one of the plastic storage covers in the rear of the vehicle.

In 2018, the SPID was replaced by a QR code label located on the B-pillar (driver's side, between front and rear doors).

Alternately, 3-digit all-numeric Sales Codes were used on Sales Order forms.

The 1960-68 models' Cowl Tags sometimes used 2-digit Group Accessory (ACC) codes (format #@, where @= 1 thru 5).

• The RPO code alphanumeric format is typically @##, but @@# also occurs, along with other more rare exceptions, including 4-digits. RPO examples include AS1 and B50
• GM didn't completely standardize RPO codes until 1969.
• RPOs may be generic (available on all models over many years), or specific (available only on specific models for limited years).
• RPOs have been reused over the years, so a specific code may identify different options for different model years.
• Most RPO codes are shared by all GM Divisions (except some early Cadillacs); the most noticeable exceptions were Division specific codes like engines (including "L##" and "W##") and certain other options (e.g. Chevrolet's Z## codes).

RPOs codes are assigned to align with specific component groups and with UPC groups as tabulated below:

A few RPO codes have become notable enough that they have been used as model names. The Camaro Z28 name came from an option code which specified a performance-oriented configuration. This happened again with the Corvette Z06 models. Most RPO codes that are promoted to model names are appearance packages only, and are not related to speed or engine performance. Two examples are the Z28 and Z71. In the 1980s one could order a Z28 Camaro with a 2.5 liter engine, although this was rare.^{[citation needed]} RPO Z71 was an off-road suspension for trucks that is not related to the drivetrain. It became notable enough to be promoted to a package name, even applied as a logo sticker onto the vehicle rear quarter body panel. Although it usually came with four-wheel drive, two-wheel drive was also available.

• L78: big block V8 engine by Chevrolet
• 9C1 (Chevrolet Police package)
• Z71: Truck Sports Package