My '65 with 200 l-6 had a Clifford dual-outlet header and a pair of Dynomax turbo mufflers for years - tailpipes out the back, of course. When you weren't in it hard, it sounded pretty good - mild V-8-ish. Wind it out and there's no doubt it's a six.
'course I eventually got bored with just sounding sorta like a 289, but accelerating like a Pinto and decided it was time to actually PUT the V-8 in.