1977 Ford Bronco rough idle. Smooth at high RPMs

This just started yesterday leaving work. Engine will run rough when ideling(when I say rough, I mean it shakes the whole truck), but as soon as you give it enough gas either driving or in park it smoothes out. The engine doesn't die, but seems as though it wants to. I rebuilt the carburetor 6 months ago and adjusted the timing. And it has run perfect until this point. The engine was recently rebuilt 1 yr ago as well and the following replaced: New spark plugs, wires, cap, rotor, coil, fuel filter, fuel pump.
The temperature has just recently dropped a considerable amount as well (-20°), not sure if that impacts any thing. Another thing I recently noticed is that if I punch the gas, every once in awhile the engine will backfire. This is my daily driver. Please help!