+1 On most of what KMP said...
Not to rain on your parade, but I'm seriously wondering if you REALLY needed the timing chains replaced at all? Sure they had 70k miles on them, but aside from your "tuner" telling you the numbers were low because of the chains, did you experience any other issues, or drive-ability problems?
Every dyno is different, you can run on 10 different dynos, and probably see 10 different results. If you look at the LLT dyno page, there are modded guys running on mustang dynos showing 20hp less than you, and there are guys with way less mods thank you running on a Mustang dyno have show 20-30hp more. Dynos, weather, location, climate, correction factor, too many variables.
I really hope all this works out for you, and my fingers are crossed you meet your goals. I don't know your whole timing chain situation, but I just kinda have this feeling that you got taken on the timing chain thing.
Here's a guy with "full bolt ons" and a tune, running on a Mustang dyno that pretty much matched the number you put down (see pic below)...
Take what I say with a grain of salt.
