I see no one posted a response! I wondered how you got on. I renovated W590 a few years ago. It too me 5 years in all and included rebuilding the 1960s collars mast. I refitted all the original fittings but now would like to fit fixed spreaders since I don’t like the way the mast wabbles at sea.
I’m thinking of buying a second hand spreader bracket, cutting it in half, drilling fixing holes at the front and packing out to get the profile right.