If you are doing it on the side of a road/bank, you might find it easier to pull the rad, disconnect the down pipe,undo the heater hoses and engine mounts and slide the engine forwards, sooner than restling with the gearbox/tf box above your heads...
If you havent got an engine hoist handy, a decent ratchet strap and a strong lump of timber or box section cut to length to sit on the inside edges of the wings will support the engine...
I would think you should be able to get the engine at least 8 inches forwards which it should be enough gap to change the clutch...just think its a bit safer and pleasant as not so much t do underneath and the box will stay in situ, and the props etc...Most of the leckies and pipes and cables should have enough movement without removal...
Just a thought anyway...tell me to shut up if you like!

You now how it is...
give a lazy man a difficult job and he'll find an easy way to do it...
Hope this helps
Gregster