Rear Independent Suspension? Anyone?

I thought My Cousin Vinny had a posi-lock rear rather than IRS,

The cousins car was a ‘63 Buick Skylark with a live axel. The Bad guys were driving a ‘63 Pontiac LeMans sporting a rear transaxle, IRS, and PosiTrack or whatever PMD called it… This was the only year Pontiac used this design.