Aside from the king pins there are a few places the steering may need some attention. Looking under the car, there is a ball joint at each hub which has a rubber cover. If either of these has split, the whole rod is best prelaced as they are self-lubricating and will have probably been contaminated. If the rubber is just in poor condition, but intact, new rubber seals can be used.
Further in towards the centre of the car there are rubber bellows on each side of the rack. These are partly filled with grease, so if they have split they need replacing. If they are dry and the rack has become stiff, then its best replaced, as worn steering is potentially deadly.
Its all covered in the haynes 126 aircooled manual 1973-87 models (you need this late version for the later steering) - available on ebay for a few quid. There is a BIS manual free online - its probably covered in that as well, and I'm sure the steering is the same for both 126 BIS and late 126 aircooled.