Rare Dodge Dart GT? Which engine is this?

Could also pop one of the valve covers and see if it has the adjustable rockers that all 273 engines had. But, I would clean off that pad on the front drivers side block, just under the head, and get the numbers there. You can rule out a 64/65 engine by simply looking at the intake bolts, a 1/2” socket indicates the smaller 5/16” threads, which are unique to the 64/65 273. And, as a matter of reference, the 64 273 was only available with a 2bbl carb. Identifying the year and displacement is easy by looking at that stamped pad tho.