If you are wanting more modern shifting on the drop bars similar to Shimano STI's, then I've never seen anything for a 2 x 5 bike. If your rear spacing is 130 mm you can put anything from 7 speed to 11 speed on the rear. However your Nishiki might only be 126mm between the drops, but that can be spread to 130 mm usually on a steel bike. Google up cold setting a bicycle frame.
If this is a touring bike and you actually use it for touring with paniers loaded to the gills, then you might want to consider 3x on the front too.
Don't try to mix and match components if you aren't experienced with understanding the spec's or even being able to find the spec's. Get everything from the same group set. And for certain don't try to use 7 speed dual control levers with a 5 speed rear.