1955 merc lower unit....swap to 1972 style....is it possible?

[oops!]

i have a 1955 merc 50 hp ...

the shift shaft system is different than the "newer" 1972 unit.

the 55 seems to have some bearings where the shift shaft inserts into the lower.

the 72 is the oppisite and a more common set up.
the casting seems to be a bit different between the two lower units.

is there a conversion kit?....or is the shift system swap not compatible?

thanks all
oops