Rivendell Silver2 Shifter

These lovely shifters have the distinctive shape and microratcheting you found on the Suntour equivalent in the eighties, will last forever, can be mounted in a variety of ways, and look amazing. 

It's a bit complex to put into words whether you should be getting the X or O versions based on your installation type but Riv's handy schematic in the product photos here should give you a good idea! They also provide excellent guides to friction shifting in general.

Match them with bar-end pods or thumbie mounts, or get 'em alone for your downtube.

Please consult this guide for lever selection depending on where you'll be putting these: