do you really want another 40 kilos of weight in the already heavy BA?
Well yeh, if its something important like fuel capacity. And when its empty the weight is gone!If you don't want the weight, you just don't fill it up as much.
I know the Utes (and wagons?) come with larger tanks. Commo's have 75litre tanks (although not all that is useable). E-gas cars have 93 and 116l tanks (so there must be some room around there for them.
75 litre verse 68 litre that could mean a extra ~100 km range per tank of fuel on the highway.
I know BMW and Merc still make big tanks, take a S class or a 7 series, 100+ litre tanks.
I've heard of people putting them in Commodores but I hadn't heard of anyone doing it with a late model falcon. I guess they don't do it anymore.