Hung, after a long conversation, many years ago, with Colin Wilson Brown, where he explained all Dato Z's are in SCb, because the bodyshell was unchanged, as t applied under GSRA.
The 2.7/3.0 Porsche's were a new body,
Same with Alfas,
The Dato Z carried the same body from end 69 to 78, hence Colin placing all the Z's in the Scb category
Save for the 2x200cc engine capacity increase, and the change from two carbs to single body injection, the Z, mechanically remained unchanged, thats the basic reason.
It's nt as ff we are geing over-run with Z's in Group S, and certainly not many 280Z's, but without the pissibility and encouragement to other potential new Z cars, including the slightly mre mdern version,, it just becomes Group Porsche.
Re the 1969 built 240Z mdel, we know they were being sold in December 69, but were not sold into the US and Australia until 1970
CAMS needs the GSRA to accept that they were sold in Japan, but this need written evidentiary proof, which s not available from Nssan
Even if it was the L20A six cylinder, the mdel run on would then have all Dato Z's in group Sb.
Cant have that now, can we!