it has original paint (yellow) and parts, basically my grandpa bought it in 66 and hes had it and taken care of it ever since, so its in pretty decent shape
oh and its a manual transmission if that makes a difference
Not enough information to give an accurate appraisal of this car.
Sounds like what i would call an unrestored survivor.
Color means nothing.
Miles make little difference on a car this old unless it has ridiculously low miles, like less than 20,000 documented miles.
A plain 66 Mustang is worth between $7500 - $15,000 for one that is in decent but not show car condition.
If it is a GT the value is between $11,000 - $19,000 for one that is in decent but not show car condition.
Add 7% for a 4 speed manual transmission
Deduct 5% for a 3 speed manual transmission
See the links below to get a better idea of the value of this car.
The third link explains the condition codes. Be honest with yourself when evaluating the condition of a vehicle. it is a very common mistake for someone to state that their baby is in better condition than it actually is. Any serious buyer will quickly spot this and walk away.
The ultimate value of this Mustang is the size of the check that someone would be willing to write you for it.