So...when I first put my boat together I had the steering assembly from a 1970 boat (castings/crossbars) and the rudders from a 1989 (black plastic). These worked great until one day I flipped the boat. Unbeknownst to me, my mast had a leak and filled with water. By the time I had flipped the boat back over, somehow the crossbar/hiking stick, 1 upper casting and part of one of the black rudders had fallen into the drink. No worries, I had backups. So since then, I've been sailing with 1 white 1970 rudder, 1 black 1989 rudder, 2 lower castings from 1970, 1 upper casting from 1989 and one from 1970. Rudders pop up all the time, I have too much toe in and it's really sloppy even with shims.
So I went and bought 2 matching black plastic rudders. Neither of them fit into my current castings, not even close. I also bought an entire 1977 boat but something was chewing on the rudders. So now I'm thinking I'll try the 1977 rudder assembly with the new black rudders. If they don't fit, I know I'll have to fill the holes and drill new ones. My question is, how could they be so different? Like the holes are at least 1.5 centimeters off. How do I know where to drill the new ones?