It all depends on what you intend to do with the car, I would at least upgrade the gearbox to the sunny 4spd. The 1200 4spds dont last too long if your ringing 2nd out all the time.

As for the diff, in my 1200 i'm still running the H145 behind my L16 with twin 40's etc. but its my daily so I dont go around doing standstills and silly stuff like that so it will last. I've just left the clutch stock at the moment so that is the weakest link and will just slip if anything and prematurely wear out, which is fine with me.

Hope that helps.

Edit: beat me to it reuby