What's strange is that the people that cut the 73's and 74's out of the muscle car era seem to be biased towards the 72's and down. It's almost an elitist argument..."mine is better than yours..." and not very accurate.
Back in the day we did things to the .318, and a lot of the emissions controls that were put on them back then were stripped off. You could do that back then. And you could take the .318 and mod it into a nice tight sleeper .340 with just a little digging around the local junkyards. I know that when it came to street light to street light racing back in the day, my RR NEVER lost, and I beat a lot of G.M.'s that were older with bigger engines. Now, that was street light to street light, and probably doesn't hold a bucket of water with some people because it isn't the track, but when you're cruisin' the hometown streets, that's solid.
I know I got a lot of DATES with that RR, and recently on FB I connected with a lot of the old girlfriends, and one of the first things they talked about was that car and how they loved it. Especially the back seat. LOL. (just had to put that in there).
It's all a matter of perspective. If you google muscle cars, you'll get the time periods 1964-1974 in the search engine return. Kinda sucks for the 1975 cars, but.... that's an argument for a different thread. Heck, you'll even get google search returns for the Muscle Car period being 1963-1969, and it ends. The problem I think is perspective... by 1973 and 1974 we had the gas crisis, and I remember the period well. Car companies started downplaying the big engines, and started advertising their cars as economically sound vehicles that could run all day on a single tank of gasoline. Fuel economy ruled back then.
But everyone who lived in the period remembers the 1974 Pontiac Trans Am, the 74 Camaro, the 74 Challenger... they were muscle cars...just like the 1973 and 1974 RR's were, and if you had the .318, you could still quickien those engines up with some .340 bolt ons that made that engine quicker than heck.
The 1973-1974 Birds, and even the Satty's, are muscle cars in my opinion, and in my life's experience. You can't change what you lived.