Low RPM stumble

Just a very late update on the problem. Have only been able to drive the car recently. The problem is getting better but still having issues I believe.

I verified the timing marks on the balancer and added a timing tape (360 balancer diameter is 7.25 inches right??? Had a hard time measuring it). The timing is set at about 22 initial and 35 all in. The car idles fine and when I quickly step on it the car has no hesitation and goes really good unlike before.

The issue I am having now is when im cruising it has a stumble still. It only happens in third gear at around 1300 rpms with moderate throttle, and past 1500-1600 there is no stumble. I do know the rear gears are severely mis-matched for the cam (2.76!!!) I am putting 4.10s in really soon. The cam really only makes power past 2400-2500 RPM so is it possible that it is lugging at that low rpm? I am also worried about it potentially detonating, I havent heard any I dont think, and looking at the plugs I dont see any specs that would mean detonation. This problem gets worse the more timing I take away.