The 1987-to-1988 boundary is not a rule that every older-body Chevrolet or GMC truck ended in 1987. GM's factory VIN legends distinguish the overlapping truck families.
For 1987, the light-duty VIN card identifies position 5 as the line and chassis type. Its explicit legend assigns R to conventional-cab 4×2 vehicles and V to conventional-cab 4×4 vehicles. Position 10 uses H for the 1987 model year. The card covers Chevrolet and GMC, with separate make/type entries for trucks, incomplete vehicles and multipurpose passenger vehicles. [1]
For 1988, position 5 explicitly identifies C and K as GMT400 conventional-cab 4×2 and 4×4 vehicles, respectively. R and V remain separate conventional-cab entries. Position 10 uses J for 1988. Thus, within this factory identification system, a 1988 R/V designation is not interchangeable with a 1988 C/K GMT400 designation. [2]
What these legends do not prove
A decoding legend is not an ordering chart. Its separate line, series and body entries do not establish that every possible combination was offered. Identify the marque, model year, body, complete or incomplete vehicle status, and sales market before applying a specification. A country-of-manufacture code does not by itself identify the sales market.
One documented carryover example is GMC's 1988 U.S. brochure. Printed page 14 describes a regular-cab V pickup with standard four-wheel drive, and its photograph and caption identify a complete regular-cab pickup with dual rear wheels. This establishes an advertised 1988 GMC offering, not its exact series or order code, actual production volume, or availability in 1989. Dual rear wheels alone are not a basis for assigning V3500. [3]
A source inconsistency worth retaining
The 1987 card's illustrative light-duty VIN contains K in position 5, although its explicit line/chassis legend lists R and V, not K. We retain that inconsistency rather than silently changing the example or using it to override the legend. A particular truck should be checked against model-specific factory documentation. [1]
Sources
[1] General Motors, 1987 VIN card, PDF page 2, upper light-duty section; imprint 9/86. GM 1987 light-duty VIN card, PDF 2, September 1986 imprint.
[2] General Motors, 1988 VIN card, PDF page 2, upper light-duty section; imprint 9/87. GM 1988 light-duty VIN card, PDF 2, September 1987 imprint.
[3] GMC, 1988 brochure, PDF page 8 / printed page 14; U.S. imprint 1865-88 USA on PDF page 11. Original brochure scan hosted by XR793. 1988 GMC U.S. brochure, printed 14 / PDF 8, XR793 scan.