Hi C&V, I've been building up a Vitus 979 frameset I purchased with Dura-ace 7400, but I've run into a problem. The shifter mounts for all of the Shimano shift levers I've seen are curved such that they fit over the bosses and are flush with the tubing of the frame. However, on the Vitus frame there is a surface already there for the shifter to press against, and this is flat (see photo)

At the local co-op I was able to find a Suntour Accushift 7s lever that mounts correctly, but I'd like to have matching shifters for the rest of the drivetrain. Is there a name for the kind of mount (or shifter type) that I need? Are there adapters?

They're called 'flat' adaptors. No joke.

The half round ones can be ground down.

Looks like the adapters are hard to find so I'll see about getting some ground down. Thanks!

If you have a set of the curved style, grinding is pretty easy. I did it on the Vitus below. I used a flat headed screw inserted from the frame side, put a pair of nuts on the shifter side to hold the piece tight, clamped the screw in my vise and used a hand grinder to grind the curve down. You only want to take it down to the lowest point in the curve.

Well that wasn't so hard.

^wrong ones

Oops, my bad. I got as far as "flat shifter tabs" and started Googling...

They shouldn't be that hard to find. They are the same "lever boss covers" used on the Shimano bar-end shifters. Shimano part number 643 4300, seen here:
https://www.velobase.com/ViewComponen...=104&AbsPos=22

Talk to any of the older, established shops in Portland. They should be able to find you some.

(FWIW: in a former life, I worked at a warehouse that sold both Vitus frames and high-end Shimano parts. These parts were a common request.)