Fender has used a couple of dimensions over the years for both string spacing and screw spacing on tremolos. The drawing shows you the differences between the various bridges, so you can be sure of getting the right fit.
We have also made a list of popular models and the suitable bridges, the list is not exhaustive and may not include your model, you can see and download the list HERE.
Callaham do not make a 2-post replacement bridge however they do make an upgrade kit which only requires that you keep the existing bridge plate and posts.
