That bolt on plate is original to the 1968 Grand series up to the 69 version which changed to the later 2-hole bracket. All grand series used the 2-bolt design caliper. That is why I think your is a very early 69. Your swing arm would be carried over from 68. Until they changed the caliper bracket design. If you can find one, it will bolt right up. They are hard to find. Even when you find one, they are pricey. The only real difference in all of them is that in 68 they used a "stop" pin. Pressed into the caliper casting. Eliminated in later years. Also, the back 1/2 of the caliper that faces the tire when mounted had either no ribs or some. 68 had no ribs. I sold one a few years ago on this site. Try doing a search in the for-sale section.
You will see what you're looking for.