Depends on the exact vintage of the body. The non-vision bodies released shortly before the first vision impulses can be milled to take vision, but I don't know who the best people to do it are. The OLD bodies (certainly anything before about #2500, maybe later) have the ball detent in a different position, so there is no space on the right hand side of the body for an eye; thus, they can not be fitted with a standard vision eye.
I don't know exactly when the changeover happened, it may be when they changed from laser-engraving to jewel stickers, it may have been before that point.