Excellent support upgrade, A+. 👍
As a note:
One of my cars already had a header panel crack.
If I would've had this support earlier it likely wouldn't have happened,
but when I do fix it this support will keep the repair stable.
Well a flipper company did, Collector's Dream Cars Las Vegas LLC.
They got 25 more overpriced vehicles for sale, if money is no object:
https://www.ebay.com/sch/collectorsdreamcars/m.html?_nkw=&_armrs=1&_ipg=&_from=
Welcome aboard James.
Unfortunately this post is 12 years old & 84 GN LT1 hasn't been online for almost 10 years.
Non AC heater boxes don't come up for sale very often but they're still out there .
Good luck with your search.