Though that picture would get you all going.
A few things - First - can not be certain when article that the picture came from, was taken. Looking closely at the picture the engines are painted a different color when compare to the balancers so it's likely during 66 production
The article does not say where the picture was taken because of the subject of the article it could be a a number of places.
The tag on the oil filter is the paper engine ID tag that we have seen also on the water pump or the coil and mounting bracket on other cars/years
The engines do not appear to be the typical production engines (though I knew the picture would be a tease) as they are equipped with 4 barrel carbs, steel intakes, chrome valve covers, narrow balancers and some or all have a tach drive dist.
Some additional details include - the carbs are bagged, fuel pump mounting point is blocked off, thermostat and water pump hose attachment points are bare metal (as expected) and the exhaust ports are tape off with a single long piece of tape. Guess this would allow the plant to place the correct, for the application, manifold at the plant
Though these do not appear to be typical they do give us a little insight IMHO into some of the practices of the time