You'll notice a big difference just going to true duals without the headers if you want to save some money.
If you do go with headers, follow the advice and get coated ones. That will pay off in the long run in heat reduction, appearance and durabiity. Block hugger type should bolt right up to the stock exhaust pipes, long-tube won't and you'll need some pipes fabricated.
Long-tube headers will provide better performance overall, but may also create ground clearance problems and maybe problems clearing the steering box. Block hugger headers don't give the performance potential of long-tubes, but more than stock exhaust manifolds, so they're a nice compromise.
A '79 L82 is a nice engine, but is still emissions controlled. My own opinion is you won't see maximum potential of long-tube headers without some serious head re-working, a camshaft and re-curving the distributor. Block hugger headers is probably a better bet for you if you do decide to install a set.
You need to really determine what you're looking for from the car first and make a plan to achieve that. Don't just start installing parts you might be unhappy with ultimately.
BTW - welcome!