Before you rush out and buy stuff, you might want to think about what your intentions are.
Do you want the bike to be fully original, built with period-correct parts or do you want to "retromod" it (finish it with modern parts) ?
In the first case, you'll need to get hold of the original speclist and then look for the correct parts on eBay. In the second case you'll still need eBay. In the third case, your only worry would be the compatability between old and new parts.