I don't know if it will make any difference but the early Mercury cars had an integral pinion and drive shaft. This shouldn't affect the installation of a Columbia OD but it can affect the situation if a person wants to change ring & pinion gear ratios. It's getting harder to find the narrow Columbia ODs but there are likely some still out there. It's a good idea to have them updated to make them stronger. This is a good link for info.
http://www.columbiatwospeedparts.com/