Question about 340 vs. 440 (From newbie)

The 340 was built as the performance motor for the 68 Darts and Barracudas. 1970 the plymouth Duster and the Dodge Dart continued to carry the 340 as the performance option. Great power to weight ratio and the price new was resonable . If you ever rode in a well tuned 340 A body youll know how they became known as "giant killer" & "big bore hunter". Big blocks were offered in the early yrs but had restricted exhaust. The 440 was not offered in the Roadrunner until mid year 69 and that was the 6 pack.
Just some info to answer the " how come"