RPOs may be generic options (available on all models over many years), or specific options (available only on specific models for limited years). 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. However 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 you could order a Z28 Camaro with a 2.5 liter engine, although this was rare. 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 rear quarter body panel. But although it usually came with four-wheel drive, you could actually order a two-wheel drive Z71.
Whipps, Kevin (2018). How to Restore Your Chevy Truck 1973–1987. CarTech. p. 71. ISBN 978-1-61325-199-7. 978-1-61325-199-7 ↩
outintheshop.com SPID Reproductions https://outintheshop.com/2.html ↩
67-72chevytrucks.com SPID pictures https://www.67-72chevytrucks.com/vboard//showthread.php?t=282003 ↩