The answer is a replacement may or may not fit the pedestal. If it's a different make, chances are it won't fit without modification - (e.g. extra silicone).
I had to replace the loo bowl due to a crack, added complication was that it's cream - the second most popular colour that's no longer available. I had to travel to a bathroom warehouse with the top of the cistern for a colour match. I did, however, have to make modifications to the flush outlet seals so the new bowl would connect water tight to the cistern.