Before you lock in Shannons, suggest you give Lumley Special Vehicles (formerly Vigil) a chance to quote, as they supported the big annual Victorian Mustang round-up back in October. Their number is 13 35 78, and they told us special deals applied to Mustangs, but I don't know how long that lasted.
Most who have tried them have saved money, and reports on claims are all good.
Might be able to claw back a bit towards those windscreens.
Incidently, have you thought of getting the rear glass polished. It's a lot cheaper than new, and generally comes up really well. I think Windscreens O'Brien do it, but not sure in NSW.