First, the headers: If you've got an old set in good shape that fits and flows well, take 'em off and send them out to be sandblasted and ceramic-coated. If they never fit very well and some of the tubes were hammered flat during fitment, junk 'em for a newer set that actually fits and spend the extra dinero for the coating. Got manifolds and want to keep them? Those can also be coated to clean up their appearance.
For pipes, many musclecar owners are fortunate enough to be able to buy kits featuring gorgeous mandrel-bent tubes in large diameters specifically designed for their cars. You can probably do the install yourself, though you might need the muffler shop to weld up the collectors and such. Make sure to use tailpipes this time.
Engine Bay Much like its interior, your car's engine bay should be functional and attractive. If your ride has been a victim of overzealous motorheads for the past few decades, there are probably all sorts of crimes being committed under its hood. This is another area where minor changes can make major improvements.
The most obvious parts to check are the valve covers and the air cleaner-if either has been in place for more than 10 years, it is likely to be rusty, cheesy, or both. Trade up from that '82-spec Taiwanese chrome dress-up kit and consider a set of cast-aluminum covers, which can be had in polished, machined, or black matte finish in a number of clean designs. The choices for air cleaners are vast, so you should have no trouble losing that mushroom-shaped Cal Custom unit. One of the hottest, though perhaps costliest, looks in accessories these days is the fabricated aluminum approach, where components are made from TIG-welded aluminum sheetmetal and left with a bare finish.
Of course, the engine itself will likely need refinishing, and here again, the aftermarket has stepped up with high-quality engine paints in all the OE colors for restorations. Or go with something a little more modern. A popular look right now is the metal-finish effect, using paint colors that mimic titanium, aluminum, and other high-tech alloys. These go well with machined-aluminum brackets and accessories, as well as the aforementioned sheetmetal parts.
Finish the bay out with cleaned-up wiring, a fresh set of modern spark-plug wires, and maybe a thermal barrier coating on your headers, and you'll no longer be embarrassed to raise your hood.
InteriorThe cockpit of a 30-year-old performance car can have many frightening, or at least, annoying features. A good interior should be visually appealing as well as functional and comfortable. The most obvious trouble spots are the seats, which might be trashed or worse-transplants from another car.
If your seats are torn up or beset with outdated custom upholstery, have them re-covered. New reproduction covers are available for most popular cars from back in the day, and even for some that were not so popular. If covers aren't offered, you can try to round up some original-style fabric or upgrade to a more contemporary cloth, though you'll probably need a trim shop to do the stitching.
If your stock seats are missing, or if you want to ditch the big, flat bench, consider upgrading to aftermarket buckets. Quite a few companies offer universal-fit buckets with application-specific mounting brackets for most cars.
But the seats aren't the only interior elements that need to be addressed. Maybe it's the cheesy aftermarket steering wheel, or the dime-store gauges, or the incredibly frustrating and equally gaudy ratchet shifter. All of these items can be quickly and easily swapped for either updated aftermarket equipment or the stock stuff you removed years ago.