318 “A” or “LA” ?

For 10 years I've owned a 1966 Polara with a 318 engine. I was always under the impression that it was an "A" engine and not the later "LA" 318. I was looking at a VIN decoder on a website that claims the 5th digit as an "E" signifies a "318 1-2BBL 8 Cylinder "LA" engine".

I believe 1966 was right around the switch from the "A" to the "LA". Does anyone have a definitive answer to which power plant is in my 1966 Polara 318.
Author: Fishfan