FWIW
Vintage Shoei hardbags, large or small, will work IF you get 'em with original Shoei brackets for a 750. The stock tail light is OK but the orig rear turn sigs will have to be removed. Almost all Shoei's (not all) I've seen have Shoei turn sigs mounted on the bags. Make sure the brackets are correct and complete. The brackets are a must!
Nice Shoei's can still be found on ebay. I found an NOS white pair of the small ones. They are now on the 550.
If you want to see a set of the large ones on a really nice 750KO, look in bike of the month for Simpson's KO. They are large but IMHO, they look like they belong there.
If you prefer soft bags, you can buy and modify later model "supports" (or make a pair) or saddlebag "brackets" (metal). They are U-shaped and support the bags from the fender side to keep 'em from rubbing anything. Ebay has lots of 'em for later bikes.
Just a thought - - -