Hi Brown,
I think you'd better check your charts again.
For your situation specified above:
Piper PA31 Navajo (wing lockers): 915 metres TODR to 50 feet @ SL
Piper PA31 Navajo (no wing lockers): 762 metres TODR to 50 feet @ SL
I haven't flown the Chieftain but wouldn't expect the distances to be less than the Navajo.
450m sounds more like a Light Seminole!
Hope that helps
Cheers
TT