AAP and the entire car part market benefited from the biggest bubble in resto car prices ever. Loads of garages opening up specifically to make and sell resto cars drove parts market.
Prices have been falling for around a year or so from crazy levels, like 100K for an old Chevy or Ford. Nowhere to go but down from here, especially with the entire economy falling too.
http://www.businessinsider.com/vintage-car-market-sothebys-2017-8