sx80 mkII

[bigbadbaz]

Hi,
My son has purchased a 1989 Toyota mkII GR Saloon(sx80 this is a solid axle type,not independent).
What I want to know is ...how hard is it to change the rear drums to disc brakes?.
Would it be easier to change the whole rear end to a later type( If there's such a thing ) like a Hilux rear diff. or maybe get axles out of a later type as long as the splines are the same.
Any help would be appreciated.
Cheers
Baz