Auto Racing: HELP!, pms system, handheld programmer

Question
The only reason I want a new tranny is cause I want to get my car putting out 300+ HP but no more then 400. Its a stock tranny so I dont think it will hold up and it shifts hard sometimes from 1st to 2nd which is weird. I love Fords but I no nothing about cars. This car is kind of like my do it yourself way of learning. So if you had my car what would be the cheapest/easiest way of tuning my car from stock to "WOW did you see that GT!". I appreciate all the help. Thank You! Im open for anything just let me know.
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-----Question-----
I have a 1995 Mustang GT automatic...its basically all stock. I was just curious on what kind of transmission I could get to replace the one that is already in there. Also if there is like performance chips that I coould get that are fairly cheap that could increase the HP and Torque of my car. I dont want to go all out right now but I want to be able to keep up with the 4.6's.
-----Answer-----
Thomas-

  I wouldn't really recommend a whole new transmission unless you're going to go from an automatic to a manual.  I would take the AODE you have in there and have it built by a company like Lentech, Art Carr, or Performance automatic.  Heck, just a good torque converter and a shift kit would give a serious difference.  As for chips...at a stock/mildly modified level chips just don't do much.  You might pick up 5-15hp if you're lucky, but chips are really more for engines that have been more highly modified and need a custom tune to keep the motor in a specific state of tune.  If you really want to change computer settings, I would go with a handheld programmer like one from Diablosport or SCT (or if you want to get a bit more advanced you could go with something like Anderson Motorsport's PMS system which is much more flexible but about twice the cost).  They'll flash the computer just like a chip, but they can be plugged in and unplugged and used over and over...a chip is burned once and that's it.  They're a bit more expensive...usually around $300-$400...but if you change the tune 3 or 4 times as you make more modifications, they easily pay for themselves.  Hope this helps.

Steve

Answer
Thomas-

 The first thing I'd do is build the engine up.  Nothing too fancy...some heads, a cam, a good intake and maybe a 331 stroker kit in it (if money allowed).  Get some good exhaust...headers, 2 1/2" H or X pipe, and some nice mufflers.  After that I'd go with 3.73 gears in the rear end and stick a 2400-2600 stall torque converter in the transmission along with a shift kit.  After a good tune and with some good tires that should be good for a 12 second car...maybe even a bit faster with the right parts, tune, and tires.  Hope this helps.

Steve