That's a pretty silly statement Dave , mopar put a bunch of 383's in cars and they were a big part of the of what made Mopars name back in the musclecar era on the street .
As far as the 2" exhaust , yes it's going to be a restriction even with the small tube headers , the factory 383 cars had 2 1/4 " headpipes and they used the STOCK 340 2" tailpipes , when I switched over to a 2.5" mandrel bent system with the stock manifolds on my Dart it woke the engine up some , it's not the fastest car on the block , but it's a lot of FUN to drive .