How to Buy Muscle Cars?

Increasingly popular with muscle car collectors are "resto-mods." As the name implies, resto-mods are restored but they are also modified or modernized. From the outside, a good resto-mod looks like a faithfully restored muscle car.

Inside, though, it might have better seats, three-point safety belts not available on the original, disc brakes where the original had slower-stopping drum brakes or other modern parts that make the car more enjoyable to drive and safer than it would have been with "correct" parts.

In most types of collecting, any change from the original detracts value and it is that way with many muscle car collectors.

"Some guys want matching numbers," Jackson said, referring to identification codes used to track cars and parts, "all the way down to 1970 air in the tires."

For some collectors, though, modifications in the interest of comfort, safety or performance can add to a car's value.

"There is a greater tolerance for modified muscle cars than there is for, say, modified '50s cars," said Hagerty.

That's because many muscle car collectors like to drive what they collect. For example, Jackson even drives his authentic '71 Hemi Cuda convertible, he said. The original engine stays in the garage, though, mounted on a display stand.

How much variation is acceptable from the original is a matter of taste. Before making any purchase of a collectible car, it is important that the buyer understand exactly what's being purchased, experts agreed.

That means asking lots of questions, checking all paperwork carefully and, all the experts CNN/Money spoke with agree, enlisting the help of a knowledgeable appraiser. Also, they said, while a well-bought classic race car is unlikely to decline in value, buyers shouldn't look at any classic car as purely an investment.

"It's primarily in the love of the car," said Brett Torino, a Las Vegas-area real estate developer with an extensive collection of classic muscle cars, including some extremely rare cars. "You don't get into it for the money."