I see you checked the cam timing. Your post says it has stock ignition. The pickup coil has a polarity, the engine will run if hooked up reverse polarity, but it will run like you describe. The stock mopar distributor has a plug so it can not be switched, but aftermarket distributors may be wound wrong polarity on the pickup coil. MSD had a tech bulletin about this problem. http://documents.holley.com/techlibrary_pickups.pdf