New Member with some questions

Greetings to all. I have a 1994 mustang gt convertable with an aode trans and just a few mods. I am trying to get her running like i had my previous mustang a 1992 lx 5.0. My first question in the transmission i have shifts very eratic. the Speedo is 10MPH slower than how fast i am really going. Car shifts into all gears and into overdrive way to quick in the rpm range. Also if you get into the throttle on the 2-3 shift it does not want to change unless u back out of the gas then it will shift. is the transmission bad or do I need sensors? Next question is my car runs hot when going down the highway but in town it runs cool. I have changed thermostat to a 180 and timing is set at 10 degrees base with spout removed. I got the car in a trade for a chevelle and i like it but i need to get it running right. Also last question for now. is there a way i can find out what ford parts interchange with the mustang. I want to upgrade a few things on the car. Car has cold air, BBk equal length headers, fuel pressuer regulator, and underdrive pullies, with flowmaster mufflers and a stock H pipe. I had a 1992 lx with alot of modifications and i want this one to be faster than it is. any help will be awsome thanks for reading....