Or use a puller - or puller + hammer. As Arwys says, there might be a ridge inside the drum, due to wear. If so, it is not sufficient to only unwind the brake adjusters, the automatic adjustment mechanism inside the drum must be released, so the springs pull the shoes together and clear of the ridge. This video shows how to do it:
The video quality is quite bad, but the first minutes explains. I know your car is from 1967, and the video deals with cars from 1993 and later, so it might not work - or you might have a similar arrangement to release the brake adjuster with the drum in situ. It is worth checking out, anyhow. I think a puller should do the trick, though. Good luck!
Robbie the Norseman 2004 V6 Roadster Sherwood green
