it almost sounds as if you need to go back to the basics.
first pull and check the gap on the plugs, spec is 0.030-0.035, it's best if you set them at 0.030 as they will wear to a larger gap. then set the points (this is assuming that you are running a point type distributor) use a dwell meter if at all possable, it is much more accurate, dwell spec is 49 to 55 degrees, again try to get it set to the lower figure. after you have set the points then set the timing, I always ran mine at 15 degrees (second mark) because of altitude, you might be best off setting yours at 10 dergrees (center mark) only set the timing after the points are set, the reason for this is that for every 1 degree of change in dwell, the timing will change 2 degrees and this will affect the way that it runs.
good luck