I have the same issue.  I ran electrical and air line to the garage from the basement, but didn't put in 220/221 before I finished the basement.  Now I want it up there for a welder.  Contemplating the same thing myself.  I might have a way to get there wihtout knocking out drywall, but it won't be easy.  I don't have a fab project right now so it's not a priority.  
I'll ask a buddy that is a builder if he knows someone.