Cam is way too big, I had the same one in a mostly stock 440 and took it out.
Car ran like crap. Mine would not idle below 1300-1500 rpm consistently.

anyway,
if the idle RPM is jumping around so will the timing. Have someone hold the throttle to about 3000 RPM and set the total timing around 37 deg. then make minor adjustments to see if the idle improves.

Triple check you have the firing order correct. Substitute another carb to eliminate that possibility, and of course look for the obvious vacuum leaks... One time I pinched a wire under the intake...