They fit lincoln y block only. I have seen them on a small block before. THAT IS THE LAMEST THING I HAVE EVER SEEN. That screams I am a piece of cheap shit who is afraid to build an actual lincoln y block cause I watch too much Hot Rod TV.
If you wrap your Lincoln covers in dryer sheets and aluminum foil and bake at 350 for an hour they'll shrink enough to fit Ford y-blocks.