I've had the same problem since I bought my 71 2 door last year. I've tried everything I can think of to fix it, but still misses. I pulled the head and cleaned the combustion chambers and valve seats, re-ground the valves, replaced everything electrical, replaced the carburetor, etc. If you get it fixed, let me know what you did. Maybe I can follow suit. The last thing I have yet to try is to replace the distributor... I just got a Duraspark II and will be putting that in soon. If that helps I'll let you know.