I was discussing split washers on the Facebook 750Four site and referenced this topic for making the washers. One contributor there Andrew Koppenhaver offered the following information about which 750s used these washers:
it's easier to remember which ones don't need them. K7/K8, and F2/F3 are the only ones that don't require the D washers. All others (the early unicorn type, dashboard type, early F type) require the D washers. That change happened sometime in 76, when they started producing the late model bikes.
but please note also that from my research on CMSL.COM, it appears the same part number 53235300000 (so same size) washers were used on 500, 550 & 750 up to 75 and in some cases part way through 76. You have to search to find the frame or VIN number to identify the cut-off. For the 750F, I saw that information on a post here on SOHC4.