When I needed to replace the freeze plugs in my 235ci I found that the plugs were the same size as a 350ci. I just bought a kit and kept the extra plugs for spares. Take a couple of measurements and check to see what other engines have the same size plugs, or just bring in an old plug to the parts store.
Yes,that's true of the block side plugs, but not of the block
end plugs for the cam. I think the 350's are larger.
