Is this the 4 speed unit that was used in the Corsair?
I will put the question to Ian Gwynne of Bill Gwynne Motorsport in Turweston, Northants.
BGM is a client to my own business. They prepare rally cars to various standards and have a lot of experience with RWD Escorts, which, I imagine, may well use that 'box or a sub-derivative of it.
One question I will be asked is this - 20 splines or 23 splines? Not sure exactly what shaft this applies to, but I've heard it bandied around here and there!!
Let me know and I'll put you directly in touch with BGM if that helps.
Regards,
Paul.