Sun Tour made many models of shifting levers, so a "generic" answer is not possible.

The "best" Sun Tour levers are still being made, the 1986 Superbe levers. Today, they are made under the "Silver" name, and sell for $38 a pair a Rivendell.

And, the "Silver" levers work well with ANY drivetrain. You can mix and match brands of chainrings, cogs, and chains. You can use five cogs, or ten cogs. No matter what drivetrain you have, the Silver levers povide swift, smooth, precise shifting.

If someone uses the Silver shifters for a few weeks, going back to STI shifting would be difficult...compaired with premium friction shifting, STI shifting is slow, crude, and clunky.