Can I use B or C body manifolds fore better flow on my sleeper GTS?

Howdy,

My no prep/grudge car is a 383 4-speed 68 Dart. It currently wears the factory exhaust manifolds on the stockish appearing 451 stroker. We are screwing together a 4.150 stroke 499" 400 block with a solid roller cam and 440 source heads. I stack a 125-200hp shot of nitrous to make things interesting. : D

With all of that said, the factory driver side manifold is starting to make me paranoid at this power level. Currently the car will make over 500whp on nitrous. I'd like to find a better flowing, less expensive to replace set of manifolds. Do I have any options here?

And to get this out of the way...no headers. I have two other manual transmission cars with stepped TTI's to tangle with. The GTS is enjoyable based on it's simplicity and ease of maintenance. I do use electric cutouts to minimize back pressure. The resto exhaust is extremely restrictive.