jgcycle

I'm continuing my 1990 Trek 330 refurbish which came with 6 speed indexed Light Action parts and wonky shifters that clamp on the handlebars (they are shimano). The shifters are goofy looking but the main problem is the thumb levers don't shift easily. I dropped some oil in them but it doesn't seem to help so I'm considering some clamp on DT index shifters for 6 speed and would like to know of my brand options - Shimano only? I saw some cheap Sunrace 6/7 speed that claim to be Shimano compliant. Any other options?

Thanks, also there are brazed on cable stops on the DT.