5.9MAGNUM EXH MANIFOLDS

This is an old thread but super interesting. So to clarify I “can” use both sided magnum logs and they will fit in my 65 barracuda with customizing? If so which years should I get after? I’m going to run a magnum 360 with eddy intake 650 Holley and stock heads and a Hughes steam roller cam. Would the logs compared to Doug’s headers be a dramatic horsepower and torque decrease?