The thing is, modern cars are just by nature faster than older cars. It's not like we're at the top of the pyramid now either, cars will proceed to get faster and cars that are lightning fast now like the GT-R will become the norm eventually. The issue with speed isn't that the engine is in disrepair, it's just that it hasn't been designed with latest technology. You can call this car beautiful, and you can build the engine so that it can be fast, but any stock iteration of the 350 from the 70's is much slower than any iteration of a 350 in 2014, and for that matter any sports car of this model year.
One big issue with mid to late 70's motors in general is the fact that all the big-name manufacturers started to put catalytic converters and other economic systems to make cars cleaner, and that just helped them get slower. You compare a 350 out of a 1967 Camaro to, say, a 1977 El Camino, like pictured here, they are still the same motor and have the same potential, but one, in this case, the 1977 version, is clogged up with all kinds of economical parts that restrict air and fuel flow, therefore resulting in power loss. See what i'm saying?