[Mondial]

The negative terminals of all three electrolytics should connect together. This point is also connected to the center tap of the power transformer, which is the most negative point in the radio.  The positive terminal of the 10 uF cap should connect to chassis, but the 78 tube socket may not be the best place. The tube socket ground is done through one of its mounting rivets, which tend to get loose over time and develop a high resistance. Better to connect to a terminal that is securely screwed to the chassis, like the ground terminal of bakelite cap 20.

It is ok to use a higher voltage electrolytic for the 10 uF cap.