Try using a set of jumper cables as temporary gounds.At one end put both to the neg term on the battery and the other end put one on the block and the other on the chassis and see if that fixes the problem

1970 Dodge Charger R/T S.E. 1969 Dodge Dart GTS 440 M-Code 1970 Dodge Charger 500 383/4-speed w/A.C.