I suspect you will want GTO because the Chevelle heater control is totally different vs the Beaumont heater control. I think the Chevelle control has 3 levers. The Beaumont has 2 levers so likely the cables won't interchange.
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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