I don't think correctly! The assignment would be for J4293. There are several transcripts and specialist articles in MG club newspapers that assign the J4293 with license plate number BL51000. Also a race report from Silverstone from June 21, 1980. Even in the MG newspaper Humbug No. 31 shows the J2 on the cover picture. Maybe someone can clarify so that you don't have to doubt.