So it's got an indexed Suntour bar end shifter on the left and a Command Shifter on the right?

And you want integrated brake levers/shifters?

Totally doable- but get the good stuff (Ultegra etc). That bike deserves it. But keep in mind you're probably going to have to replace the front and rear derailleurs and get a new freewheel or cassette if its spaced for Suntour indexing.

If that were mine- I'd go Command Shifters on both sides. I love those things and your bike is already set up for it.

I'm totally envious of your bike- congratulations, it was a great score. The paint looks great- don't repaint it- just touch up the nicks. A lot of people hunt for years to find a bike like yours in the condition yours is in.