The Skyhooks performing Jukebox in Siberia on Hey Hey it's Saturday back in 1990. Not really sure of the relevance of having a Mack on the stage but it does feature well in the clip and if you watch it through to the end the Driver is sitting in the cab. Someone may recognise the truck and know more about it.
If you read the comments with the Youtube clip there is one from Neville McDonald that says that it his dad's Mack (or questionably one he drove)??? The comments also mentioned that the studio got smoked out after it had started.
Personally I was into my twenties during the 70's and never really thought much of the Skyhooks . . . personal opinion but that doesn't mean that I didn't enjoy some of their music. They were regularly banned from Australian radio!
Which came first: Skyhooks with a Mack or AC/DC on a tray truck?
One could have been attempting to outdo the other.
Jukebox seems to have had its inspiration in Fujiyama Mama:
Easyrider had motorbikes, not trucks, but came in 1969:
and to finish, for most of us 'Born to be mild':