There is an RT81 drum brake jobbie at the local wreckers at the moment. If I am there on the weekend I could measure them up for you if you wish. Could even pull the lot off and ship it to you if they have the MS65 bearings.
Seeing as the brakes appear to be identical to a TA22, I wouldn't be at all surprised if you got the TA22 (ie smaller) bearings.
Not sure about the ball joints - didn't know there was a difference between the RT40 and RT81.
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