Well...
It could be the CV outer which is integrated into the drive stub shaft and splined drive to the wheel flange, it is not a bolt-on CV as I wish it was. It is an original 1974 ish March F2 part and both sides have been showing signs of wear for some time (years), or, most likely it is the 3 drive pegs on the wheel mounting hub that are broken or loose.
If the latter then that could be easy, if the former than heaven knows what to do, BUT it might be time to re-engineer the design to take ordinary Girling CV's which I've seen done on many cars of this era, but that will take the time and a big lathe that I don't have, but know someone who has and the expertise too.
This is the CV I refer to:
