I have a 94 3.8 mustang and want to swap it out for a 5.0 or a 351. what do I need to do with the stock computer I plan to keep it all fuel injected. can I keep my 5 speed as well and do I need to do something with the rearend?  

Here's a story from our website on a V-6 to V-8 conversion:

http://www.mustang50magazine.com/techarticles/m5lp_0206_v6_mustang_v8_conversion/index.html