Hey eightyfour, like others said, it's hard to give an opinion on the situation without knowing more of what you and your dad and your relationship is like..
Dunno, what do you think? Is your dad the type of guy who, if he does something nice for someone there are always strings attached? Or, does he seem lonely?
Might be totally wrong, since I don't know your dad, but could a possibility be that it was his way of reaching out to you, like a way of connecting with you over something he thinks you're into (working on your car)?
Me and my dad, in the past we seemed to find it hard to connect. We got on ok, but, sort of uneasily & at a distance.. but we'd get much closer when we both got involved in some project... having a practical thing to get done seemed to give us the reason to hang out and talk etc..
So anyway fair enough if you don't want the parts car, but is it possible that accepting it would be like accepting your dad? And rejecting it would be like rejecting HIM? And if so, is that what you want to do? I reckon you should talk about it with him if you can...
Also if the waste of time to go get the car is what bothered you, but then your dad went ahead and got it anyway..wouldn't it make that time even more of a waste, if you burnt the car? If it turns up, I'd just accept it (if you got space for it, sounds like you do if you're on a farm?) even if you never end up doing anything with it... Cos maybe it's not about you, but about him... Sometimes you gotta swallow your pride.. that doesn't make you a slave.. it makes you flexible and adaptable.
But yeah I might be totally off track, none of this might apply to you, I'm going on my own relationship with my dad.