I don't think that's your problem, But I did as Simon says and used the bushes out of the cam shaft,
It should be lined up to bore the holes, But I just did it free hand and took a chance. The springs and plungers
in the shoes are a lot of the trouble, The plungers must be free and the springs at the right tension.
With the shoes on the Bike but not the plates, By turning the shaft by hand, both ways, The shoes must not touch the drum, Should be about 20 to 25 thou gap between the shoe linings and the drum.
If you put the Bike in gear and move the shoes clock wise and anti clock by holding the nine pins,
You can see how the shoes move to contact the drum.
Good Luck, Bill.