Just did a search, and found a few people who had dyno'd their car on a mustang Dyno, and all were right around 260-262 HP & 270-275 ft/lbs torque.
Looks like the couple dynojet #'s I found are in the
276-280 HP range
280 Tq.
Might be good enough for a rough comparo.
If I get the car back, and it puts out 250 hp to the wheels,..I'll be pissed!