When my mechanical speedo died about 8 years ago due to the old cable binding up,the part that failed was the little square drive pin in the right angle drive.
They are designed to be a weak point to prevent cable failure.
They are also a cheap, commonly available part. Any cable maker will have them.
RHD '87 M1026
(with 4L80E Trans, 242 T/case, 12K hubs, CTIS, A2 wiring, Air Con, A2 ebrake, 9k Winch,
Serpentine Belt Accessory Drive & Eaton e-lockers)