The answer to you question is that yes you can do it, but it would be easier and cheaper if you had shimano 7 speed indexing to start with. As it is you would need a shimano index capable 7 speed freewheel or cassette,which might require a new rear wheel depending onwhat you have, front and rear derailers,and the 7 speed sora shifters. I run both STI/ERGO as well as downtube and barends,and don't have an issue with sitting to shift the latter types.I suspect the old pros probably sat too......There is a product called Kelly Takeoffs, that allow downtube shifters to be mounted adjacent to the brake levers,and some people like them. I had two sets and they are both gone, one given away and the other sold for half it cost me.