Light / Horn Switch

[Badpuppy]

Seems you're replacing an early 3-position switch (1928) with the later 4-position (TwoLite) replacement, which should work ok. There are also differences in length of the front cover. Your main issue seems to be the tightness of fit and may require more whittling of the contact body. I can't explain the horn blowing, but fitment probably has something to do with it. The horn is activated by switched ground rather than switched battery like the lights.