Tuning Questions and mufflers

[Jesse 67 c-10]

I've been moving around on the timing on my 327 to get it running the best, what I'm wondering is, when I advance it more, it picks up a lot better and has more power and throttle response, but just free reving it seems to knock or back fire quite a bit, It also hesitates a quite a bit when I first get on it, after that, holy ****!, but it'll really bog down if I floor it for example on the 2nd to 3rd shift. I can back it off till it runs smoother but it hesitates more then. Any tips? higher octane gas? shood I play with the advance curve a bit too? I have adjustable vacume advance and it's hooked up to the pass side port on my 1406. I'm suspicious about the outer ring on my balancer having slipped, and have just been going by ear, what's the best way to set the timing without a light? I've heard vacume gauge?

Also, I'll soon be puting exaust on my truck 2 1/2" duals, and I want to know some recomends for nice sounding mufflers. I don't want it too loud but not too mellow either. Anyone have a sound recording? your favorites?
Thanks lots for the help!
Jesse