Maybe the person who had it before you drove 67k miles since they had it registered. I've seen new cars (2000) models with upwards of 30k miles on them at my dealership, some people has to drive cross state alot. Or maybe it was just incorrectly as you stated. Another possibility is that the odometer was rolled back....Did carfax enter it as 120k miles after you bought it with you as the registered owner or for the last person?
Well as long as the car is in good shape that shouldn't really matter.
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'84 Mustang 5.0 LX
my LX
'89 Mustang GT
my GT