Visit
www.turbomustangs.com, they have links to most of the turbo kit manufactures. I don't usually pay too much attention to the modular stuff, but after seeing you post, I spent a few minutes doing a search into the kits available.
TDC makes kits from $3995 which is said to produce 350 rwhp to a $6995 kit that makes 800+ rwhp. I can tell you the base kit must have only been running around 6 lbs of boost to make the 350 rwhp, turn the boost up to 10 and your probably in the 425 rwhp range.
Turbolocity sells kits. Not certain if the kits they sell are their's or sombody elses, but the $5549 was the lowest priced kit I could find and it made 434 rwhp & 547 ft/lbs of torque on the lowest setting. Not certain what boost level that was, but I would imagine around 10 lbs.
Pro Turbo and some others are releasing kits later this year.
All of these kits were single turbo kits, trust me, twins might look good, but after working around them for a while, you'll wish you had went single.
Hope this helps.