Welcome to headers. First, your front springs/shocks may be culprit if they are original or weak. I don't care for these modern gas shocks you typically get at the local parts stores. I think they are too "bouncy," and they really are not custom made for the car's application.
I installed my own 3" home made pipes coming off the manifolds. 3" is big and they hung down below the car. Brand new front springs said to be for my car from NAPA. New gas shocks. Hit a good bump, road dip, pot hole, or anything that would cause the front end to bounce, and the pipes would scrape.
What I did was buy a set of 70/30 racing oil shocks. What these do is allow the front end to rise easier to shift more weight to the rear end, and then settle down at a very slow rate. I installed a set of these and my scraping problems were gone, never hit again. Car would bounce up, and then slowly settle back down without the hard bounce back down as it did with the gas shocks. Got them off of Summit, not sure what brand.
I had a mild built 400 and 3-speed manual trans and on all out acceleration the rise in the nose did not seem overly aggressive. I retained the stock front sway bar and the new springs. The drag racers usually remove the sway bar which can restrict the upward movement of the nose and they install taller lighter front springs (like 6 cyl springs) to really extend the nose up in the air. I was not looking to do that, just stop my pipes from scraping at each bump in the road.
You might consider this first before new headers - it may or may not solve your problems and would be the cheapest route to go at first -and you can use them anyway should you go with new headers. But if you do have the original springs, then my recommendation would be to swap these out for a new set that are not weakened due to age and you can order a slightly stiffer spring with the original ride height properties which will be a little harsher and most likely handle a tad bit better.