Rear wheel and swap

I am new to this forum and new to motorcycles period. I have a 1979 kz 440. I would like to do away with the spoke wheel and go with the mag. One problem it don't fit right. The mag seems to be to wide. Should I change the rear swing arm or what? Thanks to anybody who can help.

The small twins are narrower than the rest.
If your new to motorcycles and this forum,introduce yourself and maybe post some pics.
That way it will help us help you.