Ok so a bit more research on these pans and filters.
Sureshift as recommended by Monstar sells the standard Camaro pan and filter on eBay for $345 delivered which they claim adds around 1L capacity over standard VE 6l80.
https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com.au/ulk/itm/192310578127
Also available on eBay is the B&M pan, which is alloy and finned for strength and cooling.
B&M claims this pan adds 1.8qt (1.7L) over stock CAMARO pan, so it seems like 2.7L over stock VE pan. These sell from $375 on eBay
https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com.au/ulk/itm/152392981213
After reading the installation PDF on the B&M site, they recommend using a new filter of gm part number 24236931, which appears to be standard Camaro filter.
I’m really unsure as to which way to go now. The B&M unit looks great and not THAT much dearer than the sureshift Camaro pan. However, the Camaro pan is much cheaper if getting direct from the states.