Converting Old road bike with downtube shifters to bar shifters?

How would one go about it. I’d like to convert an old road bike frame with downtube shifters to a flat bar road bike with thumb shifters. The frame is steel so would it be easy to get someone to weld on two stays? that would seem like the simplest solution. Any ideas?

You can get bolt-on bits that convert the shifter bosses into cable guides. I got mine from a bike recycling place but I’m sure a decent LBS would source them for you easily.

EDIT: thinking about it I did get mine from my LBS.

excellent, glad that was incredibly simple. thanks steve
https://goo.gl/4psXZ3