1970 Mustang mach 1 cranks and runs but at low rpm sounds like it's running on less than eight cylinders, But, when given a little gas it seems to run smoothly. The timing and the carb has been eliminated as a potential problems. The wiring and plugs have been examined and checked, Since the problem seems to be associated with engine rpm could it be the alternator or voltage regulator be the problem. Any thoughts or suggestions from anyone who has experienced a similar problem would greatly appreciated,