The first 280s and the last 260s were both built simultaneously during the last 3 months of 1974. This makes a 12/74 260 2+2 automatic the rarest, and one might argue the least desirable,  of the first generation, 1970-1978, Z cars! 

14 hours ago, zspert said:

The first 280s and the last 260s were both built simultaneously during the last 3 months of 1974. This makes a 12/74 260 2+2 automatic the rarest, and one might argue the least desirable,  of the first generation, 1970-1978, Z cars! 

I don't believe that is correct. The earliest 280Z we have found is HLS30 200111 and it has a 12/74 DOM.  The late 74 260Z's with VIN's Starting at RLS30 060001 and GRLS30 015001 shared the same body as the 280Z which started production in 12/74.

1 hour ago, Carl Beck said:

I don't believe that is correct. The earliest 280Z we have found is HLS30 200111 and it has a 12/74 DOM.  The late 74 260Z's with VIN's Starting at RLS30 060001 and GRLS30 015001 shared the same body as the 280Z which started production in 12/74.

So Frankenstein found his car's fraternal twin.  Dizygotic!  (Found that when I Googled to be sure).