I saw these info on GT-R fun site written in Japanese.
Early production model of BNR32s were assembled from August 21 1989 to August 1991 with chassis number 000051-017466. Then revised model had been produced from Augst 20 1991. Another revision was done in the begining of 1993.
year/total number produced
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1989/4,555
1990/8,426
1991/7,081
1992/7,961
1993/6,204
1994/7,465