You can use ReferenceUSA to identify competitors by using the advanced search feature to filter for like companies. One can filter by geography, company size, sales, and business type. NAICS codes allow one to search for companies in the same industry.
NAICS codes to try for Used Auto Parts and Auto Recycling include 4231401 Automobile Dismantling/Recycling and 4231403 Automobile Parts - Used. Remember that these may not be the only codes that work for this project.