Yes, he raced Falcons and the Mustang at the same time but in two or three different classes. If I recall correctly, the Falcon was sponsored by Ford Australia and the Mustang was under his own race team. He moved to the XB and XC hardtops in the mid 70's and then onto the RX7. As a teenager I was a big fan of him, that tiny RX7 up against the Ford and Holden V8s, always keeping up with them but never able to win Bathurst in it.
Interestingly, the Mustang was sold to someone in NZ where it had Brut 33 sponsorship and was painted green. They took a very good looking car and made it look odd IMHO. It is now back in Oz in a family owned museum. For a while I owned a 70 Mustang fastback here in Thailand, my intention was to make it into a Moffat tribute car, but unfortunately never got around to it.