Well, I'm running a 281 motor. I don't have use of a dyno right at the moment, but when I had it here, it seemed to do well with timing locked and set at 20-21 deg. Made good power from wide open down through to 1000 rpm anyway. I played with the dist at 1500 rpm and at 1200 rpm and it seemed to like the same timing. With some better tools I can be a little more accurate the next time I have the dyno.
I changed dist last night to the 22 deg with light springs. Started with a base timing of -1 and full advance was 21 at about 1500. It ran and sounded like $h!t untill it got at least 10 deg of timing in it. That was at 800-900 rpm. This motor seems to want timing down low, but not too much up top.
Like I said, with better tools, next time I have the dyno I will be able to get more accurate, but I have a good idea what it wants right now, and that's a small amount of advance coming on quickly.