I made it out to the Dyno (Mustang) a few days ago and thought I would post my results for people thinking about similar combos in the future. I mainly used the dyno for final tuning of my VE table and then did a couple power runs to finalize my air:fuel ratio up top. The final power numbers were in the expected ballpark for this combo so I didn't sit there and try all kinds of little adjustments. Total timing was 33-34* (I say 33-34* because I went with a chromed balancer and it is very difficult to read exact!) and my air:fuel ratio was 12.5-12.75 at WOT verified by my Innovate Wideband.

Horsepower was 322 at about 5,850 RPM
Torque was 308 at about 4,000 RPM
I have read/heard that the Mustang Dynos are known to read low, some local people have told me its probably more like 350-360 horsepower and about the same for torque.

The engine itself was built by me a few years back (and will be pulled soon for my 383)

355 4 bolt main vortec block
Keith Black Hypereutectic Pistons around 10:1 CR
Trick Flow Heads I ported
1.6 aluminum roller rockers
LT4 "Hot" cam
Accel single plane EFI intake
1200 cfm 4 barrel progressive throttle body
Bosch III 30 lbs/hr injectors
AFPR set at 43 psi
Hooker Super Competition Headers (1.75 to 3")
MegaSquirt 3 Extra Engine Management Controller