833 Bearing Retainer Sizes

I am using the car as a daily driver at this time and I can not make measurments until I take the car apart. I forgot to mention that the OD unit I have is a cast iron unit, not aluminum. I do not know what size bearing is installed in my unit. Is there anywhay to mack sure I have the right parts before I tear the car apart and discover that what I have will not work? I had difficulty finding the right Z bar mount for the bell housing I have, so I would like to keep that part in place. I hope all I have to do is unbolt the installed unit and install the new 4 speed with the 4.80 bearing retainer.