Is there a simple/easy way to ID a 273 engine vs 318?

I thought it would have been common knowledge as far back as 30 years ago that Canadian 318's in 1967 were still polysphere's, speculation is that they were the leftovers from the US. If there's an example of a Windsor-made Mopar in 1967 with a small block that is an LA block (not the "A" polysphere) I'd like to know more about that.

So a curbside look under the hood is going to be challenging to ID the block (273 vs 318) other than seeing the scalloped lower edge of the valve covers which will tell you it's a polysphere but not if it's a 273 vs 318.

As to the story of this car, who in their right mind would replace a 318 with a 273 in a C-body? A convert C-body at that? Even if that happened 30 years ago, where would you get a 273 from? It would have been a no-brainer to replace it with an LA318 if anything (but a 383 would naturally been more logical).