Headers vs. manifolds

Greetings!

Haven't been back here for a long time (illness, job hunting, life). Have a question on my '73 Duster project.
Engine will be a warmed-over 5.2L Magnum, question: what should I run for exhaust? I've heard the stock manifolds will not fit the A-Body engine bay without "persuasion", but any LA exhaust manifold will work (it's been suggested to me that the 340 manifolds flow almost as good as the stock units and obviously will fit my application). Should I pursue this option giving some of the problems with headers (fitment/installation issues, leaks) or is the horsepower gain worth the trouble?

Thanks,