2000 vintage Cannondale with SRAM 5.0 3x8 gears. existing twist shifters in bad shape, had set of used ones can't find now. But they probably are pretty beat too. I want to update to trigger shift but everything in the stash is 6 or 7 speed Shimano and not compatible I guess. So I'm looking at SRAM X4 shifter set @ $28.99 any other index shifters in this price range work with this setup? Could I replace the rear derailleur with Shimano and then use a Shimano shifter, or is the rear freewheel cluster (made by Sunrace) only work with SRAM?