Super 20s came with brown leather Prestini pads. I ordered several sets from the King factory in the 1970s, and on a visit to the factory in Eastlake in 1972 the guys on the assembly line gave me some pads.
Some Super 20s had rather small flat metal resonators, riveted onto the pad through a hole in the resonator. You could see the head of the rivet. Other Super 20s had larger diameter metal resonators that were slightly domed, but not very much. The rivets were soldered to the back of the resonators, so the face of the resonator was smooth. I think both of these pads are still available from Prestini.
Original King Super 20 pads are thin, about .160" thick. If you use pads of this thickness your repad job will be much easier.
I would avoid extremely high domed pads like on some newer horns. They protrude too far into the tonehole chimney and change the dimensions of the bore. I see nothing wrong with standard plastic resonator pads. The plastic resonators have a slight dome, similar to the original Prestinis.
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