what mods can I do and stay smog legal?
 

I live in California and I own an 88 5.0 GT. I recently bought the car and am now having the engine rebuilt back to stock. I would like to build the car up but I don't know what kind of modifications I could do while still being able to pass smog. I am going to use this car as an everyday car, but I don't care how many mpg it gets. If anyone has any suggestions, please let me know. Thanks a lot!

CA 5.0 possibilities
 

I don't know what the exact CA emission laws are (visit a local MVD office to find out) but I know they're tough and that you have to have all the factory emission equipment in place, so that precludes just tearing it off. Fortunately, most emisssions equipment doesn't have a huge effect on power so that's no big deal.

Whatever you do, be sure your catalytic converters are working properly, as they do the most to reduce emissions. A well-functioning EGR , oxygen sensors (and all the other sensors) need to be in place, too, of course.

You can do cylinder head and intake upgrades as well as add an aftermarket exhaust and underdrive pullies along with the necessary fuel and spark enhancements as long as the fuel mix stays within normal range and the spark is solid. With modern computer-managed engine systems you have a lot of latitude for improving performance on your '88.

FYI: Average MPG should be around 18 on a stock, well-tuned 5.0.

if your not worried about mpg id say gears would be the first mod not that you would lose a whole lot on the mpg i like 355s on a stick and 373s on autos but you can go higher some perfer 373s on the stick and 410s on the auto there would be noticeable off the line grunt and no emission probs

I actually already have 3.73 gears and I have the stock 2 1/4" exhaust with flowmasters on them (I'm not sure which style). I have a K&N Air Filter, Bosch Platium Plugs, and a 2 or 2 1/2 inch cowl induction hood. I would like to devise some sort of plan before upgrading some parts but I dont want to waste money. I would like to replace some inexpensive parts but I dont know if it's going to give me any better performance. If anyone has any suggestions, let me know, Thanks!

There's lots you can do hp wise and still be smog legal - as a matter of fact you can even put a supercharger on stangs and you'll actually get better readings for emissions!

Big things as stated in other posts, cats, egr, good O2 sensors, smog pump needs to be functional.

You can do alot legally. The trick is to make sure that whatever parts you install have a California Air Resource Board Executive Order number (CARB E.O.#).

Take care,
-Chris