There’s probably enough Lucas dialog in the documentaries and commentary tracks to have him actually say that.
If Frink has the Monty Python and the Holy Grail DVD release with the fake out opening, he might be able to edit and lift the projectionist’s dialog. It’s sadly not on the Blu Ray, probably for licensing reasons.
https://youtu.be/_0fumVnzAuI

Playing the American Graffiti soundtrack over the Biggs scenes could work too.

Wolfman Jack could be heard on the radio in Fixer’s garage and Luke’s Landspeeder. 😃