https://earlyfalconspares.com.au/
And Early Bird Falcon Parts in Thomastown (no website) carry a wide range of stuff for early Falcons.
It's going to be a specialist thing getting parts for an XR Falcon, it's not going to be a summit racing job like the Mustang but once you know where to look, it's not going to be a problem, plus there'll be some limited crossover.
Plus you also have this forum, there's enough people with grey hair coming out their ears on this forum who know **** from clay to help with chasing up parts.
You can still buy the speedo cable and brake cables from the original manufacturer, they're still around and they still have the original drawings.
Also when you're all dead none of us are going to give a **** about 1960s/1970s Falcons and Mustangs, so don't worry too much about resale value cause in 25-30 years it'll be worth scrap value, or no one will be able to drive it because unleaded cars will be banned
