Wrong SSB-A153-1 kit ordered, please help with next steps

Hi

For my Dart 1968 I've ordered wrong SSB-A153-1 from 10` drums to disk brakes conversion kit.

Now I see that I have 9` drums spindles and:

1. Should I look for 10` spindles to be ok with SSB-A153-1?
2. If yes - can anyone share where to get it? Checked all placed I know but with no results
3. Any other options?

Thanks in advance!!