I have an 85 C/K service manual and an 88 R/V/G/P manual. they are very similar to above:
First digit, Nation of Origin 1= US 2=Canadian 3= Mexican
Second Mfr, G= General Motors
Third, Make, B= Chevy incomplete (M1031) C=Chevrolet Truck (p/us, blazers)
Four, GVW, G 8001-9000, H...