Simon
All of the second hand pintles I have come across are at least as bad as the one in your photo. We still have A12’s here – but I would not use it on my boat – and therefor can not recomend that you use it!
We have the drawing for that component – which is at least something you can go along to a manufacturer with. The dificulty will be finding some company who will do it properly from suitable materials and for a sensible price.
As far as corrosion – that is always the potential problem. The original was stainless and I am sure a replacement would last as long – it is over 50 years old after all. The key is to exclude oxygen using sikaflex and epoxy materials from those areas which are covered – and then to electrically insulate the stainless from the alloy with nylon bearings.
Trevor