This is what i'd personally do:
1. Rearend gears 3.45, or 3.73 for your 7.5" rearend, maybe even 4.10 if it's an auto.
2. Supercharger (several companies make kits for the 3.8L) and they usually come with a K&N filter. Ram air usually isn't very good because it can suck up road kill, candy wrappers, etc.
3. Dual exhaust (many companies make dual exhaust conversions for the 3.8L) - make sure you get new headers, H-pipe and cat-back if you really want a difference in power.
4. Port your intake manifold.
www.extrudehone.com - this is a process of porting that is alot more accurate than hand porting and increases airflow throw the intake.
5. Throttle body and larger injectors - not exactly sure who'd make one for a 3.8L
6. custom burnt chip - a chip will give you the most gain if you have your car dyno tuned with it.
good luck, hope this helped.
------------------
previous name: 84stangLX
'84 Mustang 5.0 LX
my LX
'89 Mustang GT
my GT