I am sitting here looking at the VIN number breakdown in both my owners manual and the Chiltons manual, and neither stipulate anything about emissions. The Chiltons manual does however, show vacuum diagrams from under the hood that do tell you what your emissions are set for from the factory.
My 86 has a code of YDW which says it is a 305 with a 4bbl high and low altitude and export with an automatic transmission alternate. The export meaning it is not meant for Calif. The same year if it had a code of YFN it says it is a 4bbl California low altitude with auto transmission.
Now for the VIN, in 1981 they changed to a 17 digit number as follows...
1GCEC14D9BF123456
first digit: Nation of Origin 1=USA 2=Canada
2nd digit : Manufacturer G=GM
3rd digit : Make and type A bus (van) B=incomplete vehicle C=truck 8=multi purpose vehicle
4th digit : GVWR/Brake System B= 3001-4000 C= 4001-5000(and so on)
5th digit : Line and chassis type C= conventional cab 4x2
K= conventional cab 4x4
P= forward control chassis 4x2
G= van, sport & cutaway 4x2
w= Elcamino 4x2
6th digit : Truck series 1=1/2 ton 2=3/4 3=1 ton
7th digit : Truck body type
0=sedan pickup
1=hi cube cutaway
2=forward control
3=4 door cab
4=2 door cab
5=van
6=surburpan
7=motor home
8=Blazer
9=stake platform
8th digit : Engine and codes G=305 2bbl
F,H=4bbl 305
L,M,P=4bbl 350
W=4bbl 454
Z=5.7 Diesel
9th digit : is a check digit (?)
10th digit : Is the yearcode B=81 through M=91 inclusive
11th digit : is for the plant location...(ex..F=Flint)
12-17 digits: is the plant sequential number.
The preceeding is from the Chiltons Manual for Full Size Chevy Trucks 80-87