You should decide early what kind of Roadrunner you want before shopping. Do you want a show winner stock car, a street strip vehicle with some mods or a casual street machine? They act differently and price ranges from affordable to expensive. Don't make the error of buying a well built street/strip car, thinking you can tame it for the street by replacing the hot rod parts with stock items. This rarely works because drivetrains are modified as complete systems. If you change the carburetion, the exhaust, intake and ignition has to change to match. A notable camshaft change usually alters everything else on the car as well. You'd be farther ahead to select a stock or mild street machine than try to make a marginal track only car livable on the street. I mention this because Mopars often participate at racing events. You'll be seeing a few of them for sale.
Modified unibodies with cage systems, four link rear suspensions and special frame connectors are usually found on race cars and these are considered irreversible changes. The classic car insurance brokers tend to classify such cars in the modified category with slightly higher premiums than stock vehicles.
Documentation and Authentication: Here we'll be dealing with spotting clones and alterations affecting value of the car. Since the Satellite shell is the base of a Roadrunner, you'll often find a reproduction for sale. The first place to look is the VIN number. A Roadrunner VIN starts with RM. Roadrunners have two basic configurations; the 383 base engine and the 440 Six Pack or 426 hemi upgrades. The fifth digit tells you the engine size. From 1968-69 the 383 four barrel used the letter 'H'. A 426 hemi used the letter 'J". New for 1969 was the 440 Six Pack which used the letter 'M'. In 1970, those codes changed to "N" for 383 Magnum, 'R' for 426 hemi and 'V' for 440 Six Pack. These are the only engines used on Roadrunners those years. Hemi and Six Pack Roadrunners share lots of details and special identifying marks useful for determining whether your vehicle is genuine or a cloned muscle car. A hemi or Six Pack Roadrunner wasn't just an engine swap deal. They shared a 26-inch radiator opening in the cradle which other Roadrunners did not get. The torsion bar rods are thicker, the rear leaf springs are different and the K frame has a welded skid plate beneath the oil pan to protect it from caving in during violent bottoming out on drives. One thing all Roadrunners shared however, are welded rear leaf spring torque boxes surrounding the front spring perches. Other special identification includes 3/8 diameter fuel lines for the hemi while the Six Pack used 5/8 diameter fuel lines. These lines are metal and go right to the gas tank. A backyard clone often skips these details and will have the smaller diameter lines intact.
The K frame with big torsion bars and welded skid plate is used on Six Pack and hemi cars.
Fully boxed leaf spring perches indicate Roadrunner bodystyle, but check elsewhere as clones will have these welded in too.
Cloning has been a problem for a long time as there are many which have been produced for personal enjoyment and have since moved into the car market place. An unscrupulous or uninformed seller may sell it as a genuine Roadrunner. Sadly, many of the formerly foolproof items of verification have been reproduced now. Indeed, it's possible to make a very good clone. Don't let a fresh paint job with lots of popular options sway you. Sometimes a clean, minimal optioned car winds up being the smart choice. These cars were stripper models until 1970. Let's examine more in depth ways to identify a Roadrunner by partial VIN numbers.
An unmolested car with minimal options is valued over a tarted up car missing its original drive line.
Hidden partial VIN numbers were used by law enforcement to track stolen vehicles. They're useful for verifying a car's identity. The rad cradle is stamped with a partial VIN which includes the engine code. Reproduction rad cradles are blank in that area unless stamped by someone after purchase. Partial VINs are also found stamped in the metal lip under the trunk weather strip rubber. You can use these last six digits to match up the engine and transmissions as well. The engine partial VIN is found on the left rear cylinder head near the bell housing flange. The automatic transmission partial VIN stamped above the oil pan rail on the passenger side. Manual transmissions have a machined pad on the passenger side of main case which identifies the model and gear set used. A partial VIN will also be on the case but not necessarily on the same side. Check both sides of the case. The engine partial VIN is stamped on a machined pad above the oil pan rail on the passenger side just rear of the engine mount. You will also find extra engine related codes on a machined pad besides the distributor. Consult a service manual for decoding the letters. This will help you find a fast flyer without having your wings clipped.
Check for partial VIN under the trunk weatherstrip rubber.