All ECM/TCMs are locked. Suncoast or Factory. It requires the correct key to unlock it. EFI has set us up to unlock Factory ECM/TCMs. Its all a matter of unlocking it with the right tools.
Why not do a light trans build and converter, skip the 6 speed crap, and get a nice tuner and lift pump. Pretty standard mods and you should be very happy running low 13s with that setup. When a full trans build was suggested, you said you were not looking to do a 10 second ride, either way, you still need more than a converter to run more than 90-100 horse over factory....
If he has a mild trans build (SC III or equivalent) and a lift pump why should he be happy with 13s? A nice EFI Live race tune from most reputable tuners/vendors will put a stock turbo truck in the mid to high 12s with a lift pump.