If it's the original AMC V8, its a 304.. i had the same issue with my AMC 360 after replacing the original ignition system with an HEI.. 4000 miles down the road it's dead.. come to find out, that the HEI distributor was not properly assembled with the gear, exessive endplay on the gear to housing caused a premature wear on the distributor gear and consequently caused the camshaft gear to also fail.. after finding a Matched gear set (Camshaft and distributor gear), i made sure the endplay of the gear to the distributor housing was within specs. haven't had any issues with it since..yet...