Besides the usual things to check you didn't mention what cam specs you're running. A big cubic inch motor with compession needs lots of duration to bleed off some cylinder pressure at part throttle or you will detonate also.You will need a minimum of 240 degrees duration at .050 lift ground on a 108 or 110 degree lobe centerline.For exaple a comp cams 292 magnum cam has 244 degrees of duration and a 110 lobe center,would be a good street/strip cam for you.As for the brown puff on acceleration -your intake probably isn't sealed properly and you are sucking
oil into the intake ports from the lifter gallery.Use a fel-pro gasket # 1230 with sealer already on it.
Perry.