Personally,I prefer the smoother sound of a single pipe than the "rough" sound of duals on an inline 6.
I don't believe tuned tube headers offer any advatage on the typical built up vintage engine.Long headers are designed to work best in a somewhat narrow RPM range,good for a higher winding 250 engine or V type,but not necessary any advantage on a 4000 rpm Chevy 235-261 or old 270-302 GMC used for the street.In fact,the tuned headers can create unwanted tuning problems with carburation on lower rpm engines.
Fentons work just fine for most guys,I built my own short tube headers from scratch.With 3/8th header flanges I never had any leaks at the head.And I don't drive vintage stuff in nasty weather,so the headers rotting out isn't an issue,at least in my lifetime,lol.
I've also found the short length headers,Fentons or tube type, tie the two pipes in to one exhaust about a foot after the header connections,provides a smooth powerful power band with no tuning issues for street use.
