Leave it six and wrap it to match. The finish is bad at this point (an assumption from your description), so the new wrap shouldn't be a negative. But, drilling is a no-no unless absolutely necessary. The six banger will play well provided the edges and shell and bed are intact. Great drums, those sixers.
To further clarify:
When you go from six to eight lugs, the hole spacing is slightly adjusted. When you add that many holes to a shell, it will be detrimental to sound and integrity.