Gear.
Do not retract the gear! Retraction will cause more drag by opening the gear doors.
The evidence has shown the gear absorbed most of the energy.
Flaps.
If you could, retract flaps to to min L/D ratio for approach i.e. F20/F10.
IMHO.
I dont think you'd have time to think about it at 400 ft.
Cheers
JO