Nice, clear Z06. I will actually be very much in the market for something similar here in a month or two. Thus, I have been exploring pretty much every C5 for sale across the country.
Pro's:
Extremely low miles
Z06
Nice mods
My biggest concerns with this car...
Stock bottom end is very sketchy making that power
Stock transmission even sketchier
Running it on 91 octane
The only real reason this car could possibly see mid 20s is because of the low miles. I've seen cars making similar power with rebuilt bottom ends and T56s selling for $15k to low 20s, but with higher miles on the body. I personally wouldn't buy this car because of the fact that the 2 most expensive modifications were not done for this car to be reliable (motor/transmission).
If he has the stock parts, I would put it back to stock, sell the parts and sell the car stock. You will get similar value because of the low miles, and the person who buys it will buy it because of that reason alone.