I understood that there was 2 different bells in use, and when I told whoever I talking with the casting # on mine I was told it was the deeper one and would not need a spacer to use on a 460. Another guy a few miles from here dong the same thing, ( I don't know the cast# on his bell) he had to have a spacer made this was a few years ago. thats about all I know about them.. or think I know