Yeah, that looks like an A (poly) block.
The A has much deeper pushrod reliefs in the block than the LA due to the poly's straighter pushrod angle.
A:
View attachment 1716270647
LA:
View attachment 1716270648
In addition, if it is an early block, the A may have an additional bolt hole/boss in the bellhousing pattern that could cause some starter interference issues when using a newer transmission. This bolt hole/boss needs to be trimmed off for starter clearance. Later poly As don't have it, though. Can't tell if your block has it, but this is where it would be:
View attachment 1716270649
Now the good news.
The poly A block will accept ALL the LA's components. Crank(with 273/318/340 mains)/rods/pistons, cam/lifters/pushrods, intermediate shaft, distributor, oil pump, pan, AND HEADS (although the reverse is not true, poly heads won't fit an LA block without major work). Deck height is the same.
And now the really good news.
With a sonic check just to be sure, poly A engines have been known to accept overbores of up to .130! No, that's not a typo. That's pushing 340 bore territory there. These things are not the LA "thinwall" type castings.