Some 69 L78 cars got the 4 core curved neck. mine has it and i know some other survivor cars that have the same curved neck.
Not all the 4spd 4.10 rear end cars have them by default either, I have witnessed some survivor cars with 4.10 rear ends with the 3 row radiator, even L89s.
so when one says only bb a/c cars and copos get them, that is not really true as a hard and fast rule.
kurt should back me up on this, but its been a while.