OPINIONS ON EXHAUST SOUND

I know they came off the pregnant truck with them in 1985. I was there. That was also the first year for tubular headers from the factory. The mufflers did not have "FLOWMASTER" stamped into the case, but had both a Ford factory part number and the Flowmaster part number. You could also get them over the counter from the dealership and they came in factory Ford boxes.
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.