Pardon the long-winded anecdote, but I recently had an issue on my '66 122s' B18 where I would have to crank for 5+ minutes in the morning before it would fire up, and then it would run rough (kind of how you described it, stumbling and wanting to die) for the first 5 miles of my 6 mile commute. When I got out of work 8 hours and +15 deg. F later, it would start up just fine. I went to statically check the timing with a 12v light bulb connected to the coil and ground with the plugs out. As I spun the engine several times, the light bulb did not light up. Opened up the dizzy (mine has no vacuum advance) and there was little to no gapping occurring at the points as the dizzy cam pushed on the arm. I adjusted the gap, re-did the static timing (there was light this time), and everything has been running smoothly since (at least related to start-up in the mornings).

Hope this helps.
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Andy - '66 122s, '89 Bronco, '03 Trailblazer