Mismatched drums won't fit

[Harpkatt]

I'm fitting hydraulic drums to my 30' model a . The fronts are sorted. I'm having trouble with the rear though. 3 of the drums look the same, the forth I didnt realize when purchased, doesn't look the same as the others and I'm having trouble fitting it over the shoes. I understand theres 2 drum styles from the era,but I thought you could use either. Any insight would be great.