Before all the guys come on here and tell you that you have to put disc brakes on, I would agree that finned would be best.
And if there's any doubt, I would order for Impala. I never trust the US sites chassis parts listings for our Canadian Pontiacs. Sometimes they are accurate but I've seen a number of them that don't have the proper parts listed for a Parisienne.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)