[Nuvistor]

C60 Bush service manual needs to be 300VAC, replace that with a 1000VDC type, 400VDC in that location across the sound output transformer is a bit too small. C57 would be better with a 630VDC type.
Otherwise 400VDC are fine and take note of Ed's advice on not disturbing the smaller capacitors. In the unlikely event of one being faulty, that can be dealt with later.