98blackgtinsc

im building my 99 gt motor now and i bought federal mogul main bearings and they all seem to be the same size, but a friend told me that the stock main bearings are all different sizes, is this true?? if so by how much, beause i put my new ones against my old, stock,ones and they looked to be the same size but i dont know if they are 1 or 2 thousands smaller or bigger. Has anyone done this and know for usre if they are different sizes or not. its a windsor built, 2-bolt main, if that helps thanks for the help.