headers vs manifolds on a 318 2bbl difference ????

I had a bone stock 318 2 barrel in a 70 Challenger. Went from not turning a tire with manifolds to a one-wheel peel as long as you kept your foot down with headers. That was enough evidence for me. That said, I still have crappy manifolds on my Duster because I'm cheap and got tired of worrying about the headers hitting on previous cars. I've been thinking more and more recently about taking the plunge again.