South African Cortina Mk1 back end change

[alan]

Hi new to  OSF I'm an old guy who served his apprenticeship  at new  Mrk 1/2 Escort times, 

Bought a recent import Cortina Mk1 2 door 1965 deluxe two  door ( ZERO RUST) running a 711M 1600 cross flow and 5 speed type 9 box

however the back  end is the Joburg a Borg Warner ( M68 ) 3.89, it's 48.5 with 9" brakes but tagging the body just a bit. Its a bit clucky inside so  proactively  purchased a complete English axel from a Tena  Mk1 

I also  have a loan ( could purchase) an Escort Mk2  Gia complete axle. 

So was thinking ( I have not stripped the axles of any yet) but counted the rotation on the Escort axle and seems to  be 4.1 -1)

Q1  what is the ratio of a standard  Tena Mk1 diff

Q2  can I fit the Escort diff ( assuming both are 22 spline)  to  gain the 4.1-1 diff if that is required

Q3 Are the escort brakes ( backplates drums etc)  a direct fit into the Tina casing retaining the Tena Half-shafts etc 

Q4 what don't I know  ( and appreciate a little knowledge is a dangerous thing )