Minor update, I got A/C bulkhead installed this weekend. Simple job, but I know they all add up!
I bought this formed plate from user Metalfab on ebay
https://www.ebay.com/sch/metalfab/m....1&_ipg=&_from=
I spent a little time trimming in up,
then laid out a slot so it would sit flush and sprayed the firewall to scrib a cut line.
Finished the rough opening with the grinder.
It took a while to get it tacked it in because it didn't want to sit flush, but once there it only took a short while to finish the welding.
I rough ground it and checked the bulkhead fit.
Pretty easy job, nothing a little filler won't hide!