Those questions tend to get a wide variety of responses from members.
When it comes to headers almost everyone will agree that you should seek a set that has heavy flanges. - They tend to give a better seal without distorting. Headers are such a pain to install that it's preferable to have a set that needs as little maintenance as possible. If money was no object I'd look for stainless steel otherwise I'd go with ceramic coated headers. There was a thread on FABO awhile back where various guys discussed how well their ceramic coated headers held up. It seems that they all are prone to rust no matter which company you buy from. My money is stretched between several different projects so the bottom line for me may not always be what performs the best. I chose a set of 1&7/8" primary ceramic coated headers from JEGS that I already had hanging on the wall here. I'm sure there are threads that discuss the benefits of different designs but ones such as the Tri-Y headers get pretty pricey. The general consensus seems to be that tti makes the best headers for Mopars. We put a set of those on our Roadrunner. On our Charger we're likely to have a custom stainless set made.
The brake booster question will get you a number of different opinions too. One of the cheapest sources is 'Right Stuff Detailing'. I chose to set up my Barracuda with manual 4 wheel disc brakes. I like the feel, there's less clutter in the engine bay, and it saved me some $$ to boot. I'm sure that some others would disagree with my choice but I'm happy with it. Rear disc conversions are pretty easy to install and you'll see an improvement in braking over the drums.
I like my 'Cuda. - But there probably isn't a single component chosen for it that was the best that money could buy. Some of my choices would have been different if cash wasn't a concern. Even when you're pinching pennies you're likely to spend more than you originally intended.