Original: The first unit to be re-engined was D6123, a further 19 machines were re-engined in 1964-1965 at Polmadie Works, along with other modifications including the fitting of four-character headcode displays in the nose ends.
Simplified: A further 19 were re-engined in 1964-1965 at Polmadie Works, with other changes made at the same time. This included the fitting of four-character headcode displays in the nose ends.