3.8 to a 5.0

If you want to put a 5.0 EFI engine in there, it's going to take a lot of work, and nickel and dime you to death. You might want to consider selling the car and buying a 5.0. These cars are getting old, and it's usually cheaper to do it that way.

Kurt
 
Yes, but don't underestimate the sheer amount of work involved. I'm sure Chythar will be along shortly to share his experience.

Who, me? :D

Just did the swap myself, it is a LOT of work. If you are not attached to your V6, I highly recommend selling it and just buying a GT. My sig below has a link to my swap thread, I recommend you read it to get an idea of the work and time involved.

You can cut the time down a lot if:

1. You have experience swapping engines
2. You have several days in a row to do the swap
3. You're not interested in cleaning/painting the donor engine

Now, to answer your question, yes a 5.0 will fit in a 94-95 V6 engine bay. 96-98 Mustangs have more parts to swap, and thus will be more work. I do not recommend doing the swap unless you have a wrecked GT or Cobra to do the swap, because there are a lot of parts you have to swap as well as the engine. Piecing all those parts together will take forever and make your project take longer.