It would have been easier to undo some things with the engine still in the frame.If you make up a chain wrench to lock the gearbox sprocket,it still won't be too hard.
Those tight nuts would include gearbox mainshaft nuts (one holds the clutch hub),crank mainshaft nuts,gearbox sprocket nut,and camwheel nuts (you don't necessarily need to remove the camwheels or their nuts).
You will definitely need a clutch hub puller and a crank pinion puller.You will most likely need a puller to remove the crank sprocket;there are 2 tapped holes in the sprocket to attach the puller.The tapped holes are probably 3/8" x 26 tpi BSC (same as head bolts),but they may be 3/8" x 24 tpi UNF.It's not hard to make a puller for this,and some universal pullers will fit.
If you decide to remove camwheels from camshafts,you'll need the correct puller to remove/re-fit them.
