Checked my spares and I only have the gudgeon fittings off the rudder stock – no pintle’s. The aluminium stock and gudgeon’s are all fairly corroded. A87 had stainless pintles when I bought her but they are for a rudder ‘box’ for a vertical lift rudder – so not much help I am afraid. If you are reusing the stainless steel pin check it for crevice corrosion in the area where it passed through the aluminium pintle body. If you do have an all stainless fitting made ensure (as Trevor mentioned) that the aluminium rudder stock is isolated from any stainless by using an appropriate insulating bush such as a nylon one. I suggest you read through the aluminium standards paper, attached to my previous reply, it lists the various grades and applications.
Cheers
Murray