"LA" engine?

Here's aquote from Allpar by Engineer Pete Hagenbush: Engineer Pete Hagenbuch said:

The LA (for Light A) engine was developed with a wedge chamber, first as a 273 cid and then as a 318. Remember, this was the time the car lines expanded to three bodies, A, B and C. The 273 was limited to the A and B bodies with the 318 or B Engine in the C Body, which was new to Plymouth at the time.