Ames sells good quality boots for full sized American cars, the Canadian cars used the same boots. They are in New Hampshire. You can also order them from several companies that sell impala parts, they also used the same boots.
Skirts also interchange between American and Canadian ponchos ( but not Full size chevies), I dont know of any steel repro but used originals and vintage aftermarket fiberglass ones (foxcraft) often show up on ebay
Are you talking about Poncho62's post saying no? He was replying about 67 not fitting 66. I think the 65 and 66 wheel well mouldings are identical, so I"m sure the skirts would interchange as well.
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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