Do you have a goal/direction you want to go, 1/4 mile time, top speed, handling, ect?
What do you have? If I remember correctly it was late 88 models in CA and 89 everywhere else before the fox bodies went to mass air. The old speed density was as fast stock, but couldn't handle any modifications. It's an easy upgrade if you don't have mass air already.
Strut tower brace, subframe connectors and upper lower control arms(preferebly the on the car adjustables)are really a must and will make a noticeable improvement to a stock car.
Ballpark of 300hp before you really need to go up from the stock 19lb injectors to 24's, or 30's if you've got the motor.
Roughly 400hp before 3"exhaust. Even stock does well with 2.5" though.
Aluminum driveshafts are cheap. Add 3 to 4 degrees of timing at the distributor. They also perform well with an adjustable timing set where you can advance or retard 4 degrees.
If you have a 5spd and haven't noticed yet, you'll never bang 3rd gear with the stock shifter, they're junk.
Electric fan and 160 thermostat will get you running a few degrees cooler.
A 351 windsor will drop in easily(they're about an inch wider) and just about anything for the f.i. 5.0 is available for the windsor too, heads, intakes, exhausts. My friend has 408 windsor with a 3spd auto and 4.88s in an 8.8 axle with 31 splines. Street legal, 295/50/15 tires...spinning pulling the driver's front tire about 6 inches runnin 5.80s in the eigth.
Beware, these cars are money pits! They're hard to break and you can never afford to go fast enough!

Like the above mentioned, there's alot of cheap bolt-ons that really wake these cars up.
There's also programable ecu's available that make them easy to tune by a competant dyno tuner.
Spike tv's hp tv had a fox with a 347, aftermarket heads, aftermarket lower intake, 8 or 8.5 to 1 compression, ect. A 350ish crank hp engine(if it had higher compression). They put a single Hellion turbo on and ended up with almost 1000rwhp, and well over 1100 on 110 octane. Extremely impressive for such a simple setup, and a testiment to how great these cars really are.
Good luck with your project.
