Same thought as Marty's post above...I hold them by the rim and lightly tap another part of the rim with my palm and listen. It should have a note and resonance on its own. In some cases even new heads sound flat. My friend taught me this...he said if I try to tune a head that sounds flat I will fight it until I pull it off.

Personally, I would only consider using a vintage reso bass drum head. Everything else I would replace, but keep em if your going to consider selling at some point.

Original heads if not dented , are great to play, the extrusion process back then was different than some manufacturers today , as they stretch on the sides so it’s harder to seat and tune new heads .
The old heads are not like that and can be tuned easier.