IIRC, mid-late '60s Imperial. The extended length is the big deal. You can measure the length you need by supporting your chassis, removing your shocks and letting the rear axle droop. Measure eye to eye and check what the parts counter guy hands you; they should extend past your max measurement but not bottom out at the minimum measurement. A/T cars will generally prefer a softer shock than stick cars for drag racing, so you might even want to go hit the junkyard with a 3/4" socket & ratchet and wrench.