Weight savings...

The timing caved and water pump in the later models are aluminum already.
The heads are approx. A 50lbs. savings. The intake is approx. a 25lbs. savings. Headers are a catch 22 since your adding twice the pipe and adding another muffler.
Exhaust manifolds are not really so heavy to begin with.

If you get an 80lbs. savings, that is about the best you can do unless your engine is an older mod. Further weight reductions can be found with light weight Alt. & P/S brackets, open air cleaner. But this is pushing the envolope.