The Fiat 850-chassis is the base for all the Grand Prix's, independent of it's manufacturer.

So here's a list of the Fiat 850 models and the chassisnumbers during the years. Unfortenately the list lacks the Fiat 850 Special, which is the original chassis. Instead I've taken the list of surviving Grand Prix to "determine" the beginning serial no of a certain year.

Fiat 850 Sedan

modelyearchassis typebeginning serial noengine typeengine displacement
850 Sedan 1971 100G 1569637 100G3.002 817 cc OHV
850 Sedan 1970 100G 1376417 100G3.002 817 cc OHV
850 Sedan 1969 100G 1339271 100G3.002 817 cc OHV
850 Sedan 1968 100G 867880 100G3.002 817 cc OHV

Fiat 850 Coupe

modelyearchassis typebeginning serial noengine typeengine displacement
850 Coupe 1971 100GBC1 340091 100GBC.040 903 cc OHV
850 Coupe 1970 100GBC1 292437 100GBC.040 903 cc OHV
850 Coupe 1969 100GBC 203339 100GC3.040 817 cc OHV
850 Coupe 1968 100GC 147146 100GC3.040 817 cc OHV
850 Coupe 1967- 1966 100GC Up to 147145 100GC.000 843 cc OHV

Fiat 850 Spider

modelyearchassis typebeginning serial noengine typeengine displacement
850 Spider 1973 100GBS1 123905 100GBS.040 903 cc OHV
850 Spider 1972 100GBS1 11006 100GBS.040 903 cc OHV
850 Spider 1971 100GBS1 90090 100GBS.040 903 cc OHV
850 Spider 1970 100GBS1 67118 100GBS.040 903 cc OHV
850 Spider 1969 100GBS1 38383 100GS3.040 817 cc OHV
850 Spider 1968 100GBS 25000 100GS3.040 817 cc OHV
850 Spider 1968 100GS 21097 100GS3.040 817 cc OHV
850 Spider 1967 100GS Up to 21096 100GS.000 843 cc OHV

Bertone Racer

Although a derivate like the Grand Prix, someone figured out these details.

modelyearchassis typebeginning serial noengine typeengine displacement
850 Racer 1971 100GBR1 89992 100GBS.040 903 cc OHV
850 Racer 1970 100GBR1 67184 100GBS.040 903 cc OHV

Grand Prix

Based on the list of survivors, I've tried to make a sort of list of beginning serial numbers in a year of production. This list is not proof, just an indication of the year of build.

modelyearchassis typebeginning serial noengine typeengine displacement
Grand Prix 1973 100GB     843 cc OHV
Grand Prix 1972 100GB 1650192   843 cc OHV
Grand Prix 1971 100GB 1581909   843 cc OHV
Grand Prix 1970 100GB 1505351   843 cc OHV
Grand Prix 1969 100GB     843 cc OHV
Grand Prix 1968 100GB 1206646   843 cc OHV
100GBC 1100777   903 cc OHV