everything evolves with time. We now have computers, smart phones, flat screen tv's and even electric cars. The 340 was a great engine in it's day, but it's day is long gone, it's the day of the new hemi's. The only reason i would even consider using a 340 was if it was some sort of collectible car, but even then, if i wanted to drive it, i would put the 340 in the basement, and drop in a hemi.
I love my little hemi dart, it starts up every time, runs like a scalded dog, and averages about 23mpg ( i got close to 27 when i drove to carlisle ), and the exhaust fumes won't melt your retinas...