I would think it's too late for tapping as the okie is now in place and you probably couldn't get down into the hole far enough to make good threads. I would just get a piece of soft steel that is mallable and a bit larger than the hole from the old dowel pin, cut it to length and drive it into the hole. You probably should drill a small, shallow dimple in the okie bushing through the hole before you insert the dowel pin. That way, the dowel will secure the tube and okie together. Put on some Permatex sealer on it and once inserted, peen the edges over of the dowel onto the tube so it won't wiggle out.
