If, when you say "grooves", you mean the square notches, I know just what you need. My 1985 Nishiki Riviera has a 3-notch design at the headset & the curve was too tight to use my Park Tool bottom bracket tool with the "tooth" at one end. However Hozan makes a double ended lockring tool with a very small radius at one end (they're sold under BOTTOM BRACKET tools). It worked great! Here's a link:

Universal Cycles -- Hozan Lockring Tool

Hozan Lock ring pliers are also a very useful tool and would work, but twice as much.