Complex sentence: The first batch of fifty locomotives were delivered between March and December 1976, numbered 35-401 to 35-450, followed by a second batch of fifty between October 1978 and May 1980, numbered 35-451 to 35-500.
Split into simpler sentences: The first batch of fifty locomotives was delivered between March and December 1976, numbered in the range from 35-401 to 35-450. These were followed by a second batch of fifty between October 1978 and May 1980, numbered in the range from to 35-500.