I would think upwards of $8-9K..
Do you know what his end game is for the car in terms of horsepower?
I know that figure is a lot, and that is why people say to sell the car. Say he does heads, cams, intake, exhaust, etc..he is looking at maybe 300 to the wheels and that motor will be running pretty high compression.
If you do not touch the motor and just do a blower you might get 330 RWHP out of the car.
If you do all of the motor work and blower you will be right around the engine swap money or more and running on the ragged edge of the car blowing up. With the motor swap it will make decent power with a tune and be a great platform for a blower down the road. Coyotes can easily push 600 RWHP with a blower and be pretty damn reliable.