I Have dismantled "2" Mk2 Escorts 1975 & 1976 which had this type of interior mirror.
I am chasing a mirror and housing replacement and am not having any luck.
Has anyone got a good mirror or know what other Ford had this type?
The section that screws up to the roof is like die cast
Has somebody on the forum an idea
thanks Jim

Well I have been into google crazy and after all that ,google sent me back to an  old thread on here 24/4/10 with GTV6.
the part number to the mirror base looks like it was also on Capri's  ARC70B  17698C
Maybe someone might have an idea now, looks like I can get similar in the U.S from a Cougar or Galaxie
Is Steve still about ?

Jim,have you tried something from a later model car?
 
If you remove the mirror body at the ball fitting,try replacing it with one from a VZ Commodore.
That was almost identical to a Mk2 Interior mirror.