short answer is yes but you would have to try realy hard.
72 volts would feel unpleasant if you had a terminal in each hand but nothing more as the current has to travel a long way, however if you moved the terminals closer together, say one on each side of the chest then this would be an extremely bad idea!
the main thing with working with car batteries in series, is if you happen to created a short circuit there will be hundreds of amps flowing across it, which will probably severly damage something, so always keep all wires properly insulated. If you are grounding the frame, you probably want to leave the grounding till right at the end, that way if you accidentaly touch a wire to the frame it wont go bang!