Actually, my two 84 GT350 fox body Mustangs, bought new off the showroom floor, both had factory tubular headers on them. The 85s were the first one with roller cams. I have no idea what mufflers were on them from factory, but the last GT350 convertible that I had did have Flowmaster 40s and a full BBK dual exhaust system, including the shorty headers and hi flow cats. I really liked the sound at idle and under wot, but they did drone pretty bad at 70 mph.
I think the 83 Mustang GT was the first time they had headers from OE.
