[wayner]

My less than reliable opinion is that there has traditionally been three markets:

1) People looking for nice drivers (I'll leave rat cars off my list).
The driver car people look at well executed upgrades as a plus, but generally don't pay much of a premium. Traditionally the upgrades my just make the car easier to sell or worth a bit more compared to one that may need those stock parts replaced sometime soon.

2)People looking for race cars.
A car like you described is likely a $40-$70k car in the eyes of someone building a track car with all the goodies. That said, race car/track car buyers still look for deals versus the actual build cost. (I'm being optimistic that it is quite a ways down the hotrod road in this example, otherwise adjust the price downwards).

3)The person who wants an unmolested car. One person's treasure is this person's trash.
Now that our cars are going up in collectible value, this category of buyer is heating up, and they view modifications as devaluing.