No Vin Stamp?

The easiest sign is the old crusty red paint. A 1972 slant would have been blue from the factory.

My big question is what color is your challenger? I used to have a 1972 slant 3 speed challenger that was petty blue (VB3). They are really really uncommon since most got turned into small blocks. If it is the same car it had the original engine in 2000 when we sold it, but I ran across someone that bought the same car with a blown engine about 8 years ago. Last I heard the car had made it from central illinois to the st loius region.