Have you taken the manifold apart, spliting the top half from the bottom?
The butterfly is welded to the shaft.
Since you have located a replacement shaft, I would try and carefully bend it back into shape. If it breaks then go for the replacement, if not, you have fixed it. The shaft is probably stronger than you think. If there is a lot of slop in the shafy to manifold clearance an oversize shaft might be a good idea. If there is a lot of black soot around the shaft, there is leakage. It is your call if you want to go through the effort to replace it, I don't think a little leakage hurts much of anything. Or, you could just find another manifold.
