I had the same problem in reverse with my 750 ACE. My Hondaline was too wide by about 1/4". I just squeezed it a little and made it fit. You can't tell the difference.
If I understand yours is too narrow. Can you put it in place and use longer bolts to pull it out, then replace the long bolts one at the time with the correct ones. Then you want need any spacers. After it is bolted in you shouldn't be able to tell the difference.
DTC