"LA" engine?

All of the Chrysler small blocks are "A" engines until 1964 when they introduced the 273. That engine is an "A" engine that was "Lightened" hence adding the "L" in front of the "A" designation.

The "Poly A" 318 was in production until 1966 here in the states. '67 in Canada.
After that, all small blocks are "LA" engines until the Magnum engine came out. 92/93.