1973 360

The other main thing that held the factory 360 and even 318 back was cylinder heads.
The reason 273 & 340 were the factory revvers, is that they had similar head flow per cid, if 318 came standard with the 1.88 360 head and 360 came with something like an SM or Edlebrock heads they all would have similar breathing potential. But very different hp potential.