They were often sold to car enthusiasts through websites such as Trade Me or Facebook, or through word of mouth, once they were rebuilt.
The bust, which involves four officers part-time, has so far resulted in 11 arrests.
Since the operation began in August, there had been a noticeable drop-off in vehicle crime in Wairarapa, Mr Miller said.
Detective Sergeant Matt Wasson said many of the people arrested were connected, although the car parts might be sourced from all over the country.
"They spend a lot of time hiding them and it's not a straight-forward process."
It was vital car buyers asked questions and were especially cautious with re-registered vehicles, he said.
"If you are buying a car ask as many questions as you can about the ownership and keep questioning the person until you are happy."
"People need to do their homework, that's the vital message. If a car appears to be tampered with they should go to VTNZ and get a thorough check."
Things to look for included new registrations, fresh paint, removed or altered vehicle identification numbers and parts irregular to the model, Mr Wasson said.
Police could impound a vehicle they believed was stolen, even if it had been on-sold to a legitimate buyer, Mr Wasson said.
Once impounded most vehicles became the property of the insurer.
Police are currently seeking a red/maroon 2001 Ford Courier double cab ute with tinted windows, registration XS6159.
-Anyone with information should call Masterton police on 06 370 0378 or Crimestoppers anonymously on 0800 555 111.