Looking at a Chrysler Labaron 1994 that only has 13,421 miles. Could it have been easily falsified?

It can be falsified. You can change out the speedo or just unhook it. I guess the only way to really tell is to do a compression check. If only driven for 13k then parked, it should be pretty close to the factory specs. If they guy unhooked or replaced it and ran it for 20 years, the compression should be lower. Look at the tires, if parked for years, they should all be weather cracked. It's a tough call. Easier to fake if you live in a non winter state. Even the compression check isn't going to be 100% if work was done to the engine. Like new rings. What state is the car in? Is the seller and older guy? Why was it parked for years?