The 440 Six Pack offers best value for rarity and performance.
When shopping for an E body, you may encounter an ex drag race car. If the car was raced in a mild class of competition where the elapsed times were above twelve seconds, it might be possible to return it to stock condition without major cost. To compete in the sub 12-second ET mark, the car undergoes too many changes to convert back to a suitable street machine. The cheap way to get into the E body is buying a 1972- 1974 model. There are less "one year only parts" to hunt down and no big block version to inflate the price.
Be aware that project cars aren't great deals if lots of parts are missing. Many body and optional parts are expensive. A 1972-74 'cuda grille is a $1,000 part. If that scares you, don't ask about six pack carbs, shaker hoods or other 1970-71 "golden era" parts. It's time to talk about "numbers matching" cars. The most expensive muscle cars are numbers matching, meaning the drive train, trim, paint and all the related pieces are the same ones that came from the factory when new. As E bodies were drag raced and abused by early owners, number matching vehicles are understandably scarce. The degree of perfection restorers take to build one of these show cars rivals that of Bloomington Gold© or NCRS© Corvette standards. These cars aren't practical for hobby usage. A car with a non original but date correct replacement engine may be a better choice for enjoyment. If you plan to restore one to concours standards, understand you can exceed the value of the car easily. That said, most of the cars available are very nice driver quality and affordable during this current market downtime.
340 cars command a premium over 383 base engines due to power and rarity.
The drive trains are pretty rugged and can take high miles if maintained. It's the body you have to watch out for. Keep these in mind and you'll be able to pick a primo pony car.