Looking for information on how to convert final drive from belt to chain on a 81 cowpie,

I have purchased appropriate sprockets and a bearing brace. The brace doesnít fit properly Iím going to assume because of the longer shaft.

Anyone have information on how to do this properly? Is a shaft swap the only way?

If itís too much work for now, is there a brace to buy to run with an open primary and final belt drive?

Thanks!