1st question.
What, if anything,, needs to be done to put a small turbo on the 2.5?

2nd
Does the 2.5 share the crank position sensor ignition system from the 2.3 8 plug?

 

You have a 2.5l SOHC Lima engine, same as the 2.3l SOHC Lima with a longer stroke, same head and pistons, different crank and connecting rods, so "stroked" 2.3l

1995-1997 2.3l used the same crank sensor type and setup(0.5vAC to 7vAC) tone wheel, as the 1998-2001 2.5l
1989-1994 did NOT, they used a different type of sensor(12vDC on/off) vane window
The two are not compatible/swapable, you need to change computer and wiring

You can look at universal turbos kits, the 2.3l Lima kits work on the 2.5l Lima as far as the "plumbing"
Mustang forums might be a better place to get specific info on turbo charging the 2.3l Lima engines