Again, don't waste your time with a shift kit!!! Spend the extra dollars on a purpose-built performance valve body - you won't regret it. The difference is like night and day. Both Performance Automatics and Lentech make great performance valve bodies for your car. They have plenty of info on their websites.
http://www.performanceautomatic.com
http://www.lentechautomatics.com
A torque converter is a must if you plan on putting in a blower. Precision Industries specializes in after-market torque converters for Mustangs. Art Carr also makes great TC's. Again, check their websites for details.
http://www.converter.com
http://www.artcarr.com/catalog/ford.html?
These mods do not give you more horsepower, but they do give you faster shifts and a higher rpm launch. You wont' see any gain on the dyno, but you should shave around .4 off your ET.
Especially when you get your dyno-tune after the blower install. Get it done by someone who really knows what they're doing and they can adjust your line pressure and shift points to really take advantage of the valve body and TC with all that blown HP.
Cooling fan? You will want to invest in a
tranny cooler. There are a lot of choices out there, and its much cheaper than either the valve body or the converter.
But, then again, you plan on putting in a blower. You might want to think about a new radiator - Fluidyne makes a radiator with a built in
tranny cooler for you car. Maybe overkill, maybe not....
transmission set-up. help me out 
