Depends on what your skill level is.

In general, the easiest kit to assemble is a rebody that goes on a chassis that is not stretched or shortened; it involves replacing body panels (or the entire body), paint, wheels and tires, and that's about it. The downside is that some of these kits don't end up looking exactly like the car they're replicating.

The next easiest kit to assemble is a rebody that goes on a chassis that is stretched or shortened; it involves either removing a section of floorpan (Porsche Speedster, 917, etc) from an existing chassis or adding a section behind the cockpit (Diablo, Countach, etc), then adding the body. These kits end up looking pretty much like the car they're replicating.

The next easiest kit is a custom chassis full kit (Cobra, GT40, Porsche Spyder, etc). You hang all the suspension, mount the drivetrain, install the interior and body, add paint, wheels and tires and you have a car. Some of the kits that are easier than others.

The next easiest kit is a turnkey-minus (Superformance Cobra, Beck Spyder, Backdraft Cobra), which - as the name implies - is pretty much turnkey. The "minus" is that the drivetrain is not installed; you have to do that yourself.

After that, you're looking at a turnkey car; a car that is complete, finished, and all you have to do is get in and turn the key.

Another option is to get someone to build the car for you, which can be as inexpensive as a few thousand dollars, or as high as the sky - it all depends on what you think your time is worth; your sweat equity.

If you're looking for a specific type or style of car, please feel free to post it. It's easier to help you out if we know what kind of look you're going for. Hate to be telling you which Diablo is the easiest when you're looking for an Auburn replica...

Hope that helps.

Your pal,
Meat.