Had a true POS company van like that. I took packing blankets and spring clipped them to the roof cross member behind the seats. Got it down to a dull roar. While it's all stripped out consider routing some ENT(Smurf tube)
that the communication techs use to run wire through. Run pull string through it. You never know when you will want an extra wire.
Good luck with the project.
Vanna
Threaded Mode
