JB25, this post-
Is the most relevant, nearly all (I think it is actually all) the EE507 traction motors used in the 455s (and various bits of underfloor equipment such as compressors etc) were recovered from withdrawn 405 (4SUB) units and sent to York for reuse in the 455 units.
The traction motors were reworked/ rewound enabling extra field weakening to take place so the units could reach a higher attainable speed. Well over 80 is possible (so I have been told
) but I have never been over 75 obviously! 
The Southern region used to reuse a lot of their trains in the new builds up to and including complete chassis.
Then there are the traction motors. GEC507s (some?) of which were re-used from mid 1940s 4-SUBs.
Is the most relevant, nearly all (I think it is actually all) the EE507 traction motors used in the 455s (and various bits of underfloor equipment such as compressors etc) were recovered from withdrawn 405 (4SUB) units and sent to York for reuse in the 455 units.
The traction motors were reworked/ rewound enabling extra field weakening to take place so the units could reach a higher attainable speed. Well over 80 is possible (so I have been told
The Southern region used to reuse a lot of their trains in the new builds up to and including complete chassis.