Help identifying these LA 360 Heads.

Hey there,
First post. Long reader.
Buying my first classic--73 Duster with LA360 swapped.

First, ignore the butcher paint job on this block. Not my fault!
Second, I cant identify these heads-- I checked between the spark plugs and there's only a '31' on the drivers side and a '27' on the passenger side. No X, J, U, W... etc...

Can someone figure out what they are? Cant open them up quite yet.

Thank you,
Ben

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You'll want to get rid of the air cleaner (and maybe the Holley underneath it too) one backfire and the foam air cleaner element melts and right down the carb it goes.