What would it take for me to take the fourth gear out and swap it for something around .50 instead of .70? Like computer-wise would anything need to be done?

 

The short answer is that it is not possible to change only one ratio. In an automatic all gears are in mesh all the time, so to change any ratio you need to change all of the ratios.

You could change your gearset to an AOD gearset. That will get you a .66 overdrive ratio. It will also change first gear. The 4R70W has a higher ratio first gear, so you will lose some off the line acceleration.

 

http://www.gearvendors.com/