I specialize in these conversions, my suggestion to you would be to use SCHUMAKER CREATIVE SERVICES, TRI-Y Underchassis HEADERS.
The factory 383 Exhaust Manifolds are too expensive, and too restrictive ( you will lose 30+ horsepower, and they can't be used with power steering.
The factory manifolds are very prone to crack, very hard to change spark plugs, and almost impossible to change starter motor.
I am just trying to help you out
mopar charlie
727-271-5068