convert down tube shifter to bar-end shifter

Is it possible to convert the suntour down tube shifters (2 chainring in
the front and 8 at the back) to bar-end shifters? If so, any
recommendation?

Easily. You can buy bar end pods from Rivendell that will take your DT shifters
and put them on the end. Or use Campy or Suntour or Shimano bar ends.
Phil Brown