OK, let's go through this: We know it's not wires and plugs, the coil would effect all cylinders, not just 1 & 2. Could be the distributor cap, but not likely. Backfiring is sometimes a symtom of either valves not opening or lean mixtures. So check the valve lift on #1 & 2 to make sure a cam lobe isn't down. That's not likely either because of the good compression. If the backfireing and missing is due to a lean mixture it can't be the carb since not all cylinders are involved. I would look for a vacuum leak somewhere near the #1 and 2 intake runner. Maybe a loose fitting, cracked line or the gasket itself. Squirt a little oil around the manifold to head joint while the engine is running and let us know what you find.
