That boat looks like it's been sitting for years, you will be lucky to get it out of the field on the current tires. I would pull the wheels, grease bearings, get new tires and maybe rent a motel room for the night before trying to move it..
I put ball valves in mine 2 years ago and they did fine last winter, can't comment on the longevity but at least you can reach them easy enough and still rod them..
My last sailboat was an Oday 27 and a keeper. I recently gave her to a boy scout camp. I'm old and she still has another chance to make some kids happy. Oh, and she could out sail Catalina 27s on most any day...
I may be wrong, but I think the galvanic difference would accelerate corrosion of the cast iron...May not be enough to matter considering the normal life span of either part..
