Do it! Get a dragon performance box (adjustable) and an ar35 from the 3ltr (any).
If I crank my box up to the gigawatts and leather it I get low 20's

Day to day I get 33-36 with it turned right down - but still very quick!
The oil pump is actually in the box itself AFAIK.
You basically put the car on axle stands,
unbolt the propshaft,
unplug all the sensors
undo the T/C from the peepe hole
undo the box, lower the ar25, bolt the ar25 bellhousing on the ar35 (easy job).
One thing that might be worth doing while the new box is off the car is replacing the thrust washer (theres a how2 on here) and replacing the neck seal.
You use your original T/C and loom.
Then refitting is reverse to removal.
It's a job that first time will take you 4-6hrs all in - absolute max.
Have 2 x trolley jacks for lowering the box from the car and be prepared to swear alot and grit your teeth...
Be worth it though!
