1975 360 block info.

There is nothing special about a ‘75 engine, zero, zip, nada
except that it isn't a 71 to 74 block and it isn't a 76 and later block. I'm not looking for special. I'm looking for info on why it's a one year only and if it is considered a good starting point or if it's a less desirable starting point. And what and why it's a one year only deal. Someone knows.