I don't know if you are friction or index shifting with those levers. If you are friction shifting, you can index shift if they are 7 speed down tube shifters by using an alternate cable routing.

I am running an XTR rear derailleur with Dura Ace down tube index shifters and they are wonderful shifters; you'll never sneak up on anyone because the audible click is so loud... lol. Check out Sheldon Brown Dura Ace if you need more info.

John