Transmission output flange question
 

Hi, just bought a replacement engine and tranny for my car. It's a 70 engine with a 911 (not 901) transmission. On inspection I found that the differential was in two pieces and the cover plate was cracked where the seal sits. So, I have since sourced a replacement 911 transmission. However the output flanges on the new transmission measure only 95mm, as opposed to the flanges on the old transmission which measure something like 120mm (haven't been able to acurately measure until I remove it).

So, does anyone know why they would be different sizes? And if the shafts are the same length and diameter can I simply swap them out?

Secondly, can anyone shed any light on why the original transmissions differential would break in half, as I've never come across that problem before?

Any help would be much appreciated.

Adam