From what I understand, when running factory exhaust manifolds, you’re better off with a 112-to-114 centerline.
Also, as already mentioned in this thread, go with a custom cam for your application.
In my 383, I’m going with a Mr. SixPack custom grind from Engle Racing Cams which is designed by Bob Karakashian. The cost is a bit more than an off the shelf cam but worth it. $235.00 to your doorstep and that dose not include lifters.
But that cam has bone stock 440-6s running in the high 11s on factory polyglass tires. You might be able to get the ETs you’re after with you're 383.
You can give Mr. Karakashian a call and he’ll talk it over with you.
Mr.6Pack Racing Engines - link