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

I'm looking at a '67 Windsor-built car that the VIN says had a 318 (which means it would have been a polysphere).

The current owner (who to me has an unknown level of familiarity with vintage Mopar mech/tech) says the car has a 273. Maybe someone told him that, and he doesn't know any better. I don't know.

I haven't been to the car, it's a bit of a drive for me.

Is there an easy way to know if it's a 273 vs 318? I have an LA318 in one of my cars and I know it's impossible to see any block stampings with the exhaust manifold in the way.
NOT MINE - 1967 Monaco convertible $5000 CDN

The owner has posted in that thread and it sounds like the 273 was installed to replace a 318 by a previous owner.