I find hard to believe that there are only 2700 MMs left. Yes, we lost quite a few over the years, but not over 8500 cars. By the same math there should be less than 500 SS impalas left from the 90s. And I see those things everyday.
As for fake Marauders, there is one thing I love about these cars, Ford Vin coded them. The 03s are slightly easier to fake to the untrained eye, body code is the same as a GM LS, but the 8th digit in the Vin is the car's engine. 4.6 DOHC. "V". All other panthers have a "W" for the 4.6 SOHC. In 04 the Marauder got its own vin code. But still, 8th digit is your friend. No "V" no Marauder. Also the 4.6 4v is kinda pricey to try to fake a Merc. The LT1 is dime a dozen, the 4.6 DOHC came in only 6 cars. SVT Mustang, Mark 8, Continental, Aviator, and the Marauder