The universals are peined in, which is where they fold over the metal of the housings to retain the uni. This was so you had to buy a complete new tailshaft. The best replacement uni's are the standard 1200 ones, but you need to get the front & back fittings machined out to take the new uni's. You also need to get the rememnants of the old unis out, usually at the same time. Personally i would cut the uni's so you'd end up with a front yoke, tailshaft & a rear yoke, then take those along to the tailshaft place,as this would probably be the first thing they would do. Unfortunately this immobilises the car, as you no longer have a tailshaft. Early Datsuns use the same uni's as HQ-HZ Holdens, so the replaceable uni's are readily available. After this first bit, the replacement of uni's is like any other car.