Removing 08 Scrambler Header Nuts And Studs

My Scrambler has the factory-fitted Arrows 2 into 1 exhaust. The right hand manifold studs and nuts are very corroded so I want to replace them. However, the upper stud is tucked close to the top engine mount and the lower behind the pipes.

I can just about get a swan neck spanner on the lower nut but can't move it far. Is there some clever trick or a special tool which enables the nuts and studs to be removed (and new fitted) or is it really only possible by dropping the engine??

Any tips very welcome!