Can anyone explain where to read to understand the difference between
37
47
57
87
Since the second and third digits seperate sportsroof and non-sportsroof.....

Code Body style
35 4 dr. Sta. Wagon 2-Seat
36 4 dr. Sta. Wagon 2-Seat
37 2 dr. Hardtop Coupe
39 4 dr. Hardtop 4 window
47 2 dr. Hardtop Coupe
55 4 dr. Sta. Wagon 2-Seat
56 4 dr. Sta. Wagon 2-Seat
57 2 dr. Hardtop Coupe
65 4 dr. Sta. Wagon 3-Seat
66 4 dr. Sta. Wagon 3-Seat
67 2 dr. Convertible Coupe
69 4 dr. Pillar 4 window
77 2 dr. Plain Back Pillar Coupe
87 2 dr. Plain Back Hardtop Coupe

 

Sorry, you have that wrong.
The first position is the GM division - 3 = Oldsmobile
The second and third positions are the model line - 36 = Cutlass, 44 = 442, 48 = Vista Cruiser, etc.
The fourth and fifth positions are the body style - 67 = convertible, 77 = Sport Coupe, 87 = Holiday Coupe, 57 = Holiday Coupe (notchback), 55 = Vista Cruiser 2-row, 65 = Vista Cruiser three row, etc, etc.
The sixth position is the model year
The seventh position is the assembly plant