This is for a Beaumont? It makes a difference, Acadian and full size have manifolds over the plugs, Beaumont manifolds are under the plugs so the wires are shorter.
I got AC Delco for my Strato Chief. I can find you a part number once I know for sure which application.
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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)
89021170 GM long number, 908W AC Delco number is what the Delco website says but it had a mistake on it when I got my Strato Chief wires, so see if you can find them locally and look at them before you buy to see if they are right.
The listing for mine was for a wire set that was way too short on the first try.
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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)