I have a 1987 Series 4, it was originally an auto that I have swapped a manual gearbox into. I have since changed the rear diff to a shorter ratio manual LSD and have also replaced the driveshaft with the thicker manual one.

The problem I am having now is that the driveshaft seems to be slightly to long. When I go to put it in there is not much clearance between the diff input flange and the driveshaft flange even if I push the driveshaft as far into the gearbox as I can. I can just get it on but levering the rear subframe away from the front of the car but it doesn't seem right to need to do this. Anyone know what the clearance should be, I was thinking I may get my driveshaft shortened...

 

Make certain you have the correct shaft.
Here's the US specs for all three mm (in):
Overall length from tip of yoke to back of bolt flange:
N/A M/T 967 (38.07)
N/A A/T 913 (35.94)
Turbo M/T 966 (38.03)

U Joint Center to Center:
N/A M/T 782 (30.79)
N/A A/T 733 (28.86)
Turbo M/T 774 (30.47)

Diameter:
N/A 57 (2.24)
Turbo 75 (2.96)

Hope this helps