Do try to find the Rc car that fits your desire to to accomplish the task you have in mind
The car you need would be classified as antique very early RC stuff and may have a big price tag to its age
There is an RC car foram right on this site but they deal with more current equipment

You could always buy your dad a very nice newer higher tech car that somehow i am very sure he and you could have a real good time with

You know just maybe your dads dad thought that the car he gave your dad was not age apropriate and that he would get hurt or damage the car to easily
it could have been more of an adult toy than for a child as it was given to another adult
So the real issue was that your dads dad made a bad purchase for the child
Just saying sometimes things are not what they may appear but there should have been some communication on your dads fathers part i would think

Hope you come up with something nice for your dad as you are being a very thoughtful son and you are about to make a very bonding memory fornthe both of you - just love it !!

Happy New Year

Enjoy