@MopaR&D
My post was irrespective of emissions equipment. I'll wager not one in a hundred of us consider it when we hop our cars.
My post was comparing a well-built, alloy-headed, hi-compression, small displacement, V8 of yesteryear, to a similar displacement, highly regulated, over complicated, engine of today, in the fuel-economy arena only, and at about the same weight; sorry if that was unclear.
If I, a common uneducated country-boy hick, can get 32mpg out of a 6 liter 1960s tech engine; and modern cars are doing that but with 2.5liter 4-bangers, and it's 55 years that have elapsed, you gotta suspect something. And when you consider that this 6 liter makes 335 NA hp with just a carb swap, com'on; Somebody is holding back.